Last Friday of each month

Task

Write a program or a script that returns the date of the last Fridays of each month of a given year.

The year may be given through any simple input method in your language (command line, std in, etc).

Example of an expected output:

./last_fridays 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Related tasks

360 Assembly

The program uses one ASSIST macro (XPRNT) to keep the code as short as possible. <lang 360asm>* Last Friday of each month 17/07/2016 LASTFRI CSECT

        USING  LASTFRI,R13        base register
        B      72(R15)            skip savearea
        DC     17F'0'             savearea
        STM    R14,R12,12(R13)    prolog
        ST     R13,4(R15)         " <-
        ST     R15,8(R13)         " ->
        LR     R13,R15            " addressability
        L      R4,YEAR            year
        SRDA   R4,32              .
        D      R4,=F'400'         year/400
        LTR    R4,R4              if year//400=0
        BZ     LEAP
        L      R4,YEAR            year
        SRDA   R4,32              .
        D      R4,=F'4'           year/4
        LTR    R4,R4              if year//4=0
        BNZ    NOTLEAP
        L      R4,YEAR            year
        SRDA   R4,32              .
        D      R4,=F'100'         year/400
        LTR    R4,R4              if year//100=0
        BZ     NOTLEAP

LEAP MVC DAYS+4(4),=F'29' days(2)=29 NOTLEAP L R8,YEAR year

        BCTR   R8,0               y=year-1
        LA     R7,44              44
        AR     R7,R8              +y
        LR     R3,R8              y
        SRA    R3,2               y/4
        AR     R7,R3              +y/4
        LR     R4,R8              y
        SRDA   R4,32              .
        D      R4,=F'100'         y/100
        LA     R4,0               .
        M      R4,=F'6'           *6
        AR     R7,R5              +6*(y/100)
        LR     R4,R8              y
        SRDA   R4,32              .
        D      R4,=F'400'         y/100
        AR     R7,R5              k=44+y+y/4+6*(y/100)+y/400
        LA     R6,1               m=1

LOOPM C R6,=F'12' do m=1 to 12

        BH     ELOOPM
        LR     R1,R6              m
        SLA    R1,2               .
        L      R2,DAYS-4(R1)      days(m)
        AR     R7,R2              k=k+days(m)
        LR     R4,R7              k
        SRDA   R4,32              .
        D      R4,=F'7'           k/7
        SR     R2,R4              days(m)-k//7
        LR     R9,R2              d=days(m)-k//7
        L      R1,YEAR            year
        CVD    R1,DW              year: binary to packed 
        OI     DW+7,X'0F'           zap sign
        UNPK   PG(4),DW             unpack (ZL4)
        CVD    R6,DW              m : binary to packed 
        OI     DW+7,X'0F'           zap sign
        UNPK   PG+5(2),DW           unpack (ZL2)
        CVD    R9,DW              d: binary to packed 
        OI     DW+7,X'0F'           zap sign
        UNPK   PG+8(2),DW           unpack (ZL2)
        XPRNT  PG,L'PG            print buffer
        LA     R6,1(R6)           m=m+1
        B      LOOPM

ELOOPM L R13,4(0,R13) epilog

        LM     R14,R12,12(R13)    " restore
        XR     R15,R15            " rc=0
        BR     R14                exit

YEAR DC F'2016' <== input year DAYS DC F'31',F'28',F'31',F'30',F'31',F'30'

        DC     F'31',F'31',F'30',F'31',F'30',F'31'

PG DC CL80'YYYY-MM-DD' buffer XDEC DS CL12 temp DW DS D packed (PL8) 15num

        YREGS
        END    LASTFRI</lang>

Output:

Ada

Uses GNAT. Applicable to any day of the week, cf. [[1]].

<lang Ada>with Ada.Text_IO, GNAT.Calendar.Time_IO, Ada.Command_Line,

 Ada.Calendar.Formatting, Ada.Calendar.Arithmetic;

procedure Last_Weekday_In_Month is

  procedure Put_Line(T: Ada.Calendar.Time) is
     use GNAT.Calendar.Time_IO;
  begin
     Ada.Text_IO.Put_Line(Image(Date => T, Picture => ISO_Date));
  end Put_Line;
  
  use Ada.Calendar, Ada.Calendar.Arithmetic;
  subtype Day_Name is Formatting.Day_Name; use type Formatting.Day_Name;
  
  T, Selected : Time;
  Weekday: Day_Name  := Day_Name'Value(Ada.Command_Line.Argument (1));
  Year : Year_Number := Integer'Value (Ada.Command_Line.Argument (2));

begin

  for Month in 1 .. 12 loop
     T := Time_Of (Year => Year, Month => Month, Day => 01);
     while Ada.Calendar.Month(T) = Month loop

if Formatting.Day_Of_Week (T) = Weekday then Selected := T; end if; T := T + Day_Count(1);

     end loop;
     Put_Line(Selected);
  end loop;

end Last_Weekday_In_Month;</lang>

Output:

>./last_weekday_in_month friday 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Basically the same as the "Find the Last Sunday Of Each Month" task solution, uses the Day_of_week and isLeapYear procedures from the the day-of-the-week and leap-year tasks (included here for convenience). <lang algolw>begin % find the last Friday in each month of a year %

   % returns true if year is a leap year, false otherwise       %
   % assumes year is in the Gregorian Calendar                  %
   logical procedure isLeapYear ( integer value year ) ;
       year rem 400 = 0 or ( year rem 4 = 0 and year rem 100 not = 0 );
   % returns the day of the week of the specified date (d/m/y)  %
   %         Sunday = 1, Friday = 6, Saturday = 0               %
   integer procedure Day_of_week ( integer value d, m, y );
       begin
           integer j, k, mm, yy;
           mm := m;
           yy := y;
           if mm <= 2 then begin
               mm := mm + 12;
               yy := yy - 1;
           end if_m_le_2;
           j := yy div 100;
           k := yy rem 100;
           (d + ( ( mm + 1 ) * 26 ) div 10 + k + k div 4 + j div 4 + 5 * j ) rem 7
       end Day_of_week;
   % sets the elements of last to the day of the last Friday   %
   % of each month in year                                     %
   procedure lastFridays ( integer value year
                         ; integer array last ( * )
                         ) ;
       begin
           integer array lastDays ( 1 :: 12 );
           integer m;
           % set ld to the day number od the last day of each  %
           % month in year                                     %
           m := 1;
           for ld := 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 do begin
               lastDays( m ) := ld;
               m             := m + 1
           end for_ld ;
           if isLeapYear( year ) then lastDays( 2 ) := 29;
           % for each month, determine the day number of the   %
           % last Friday                                       %
           for mPos := 1 until 12 do begin
               integer dow;
               dow := Day_of_week( lastDays( mPos ), mPos, year );
               % dow     = 1 Sun, 2 Mon, ... , 6 Fri, 0 Sat    %
               % change to 2 Sun, 3 Mon, ... , 0 Fri, 1 Sat    %
               dow := ( dow + 1 ) rem 7;
               % offset the last day to the last Friday        %
               last( mPos ) := lastDays( mPos ) - dow
           end for_mPos
       end lastFridays ;
   begin
       % test the lastFridays procedure                        %
       integer array last ( 1 :: 12 );
       integer year;
       year := 2020;
       lastFridays( year, last );
       i_w := 1; s_w := 0; % output formatting                 %
       for mPos := 1 until 12 do write( year, if mPos < 10 then "-0" else "-1", mPos rem 10, "-", last( mPos ) )
   end

end.</lang>

Output:

AppleScript

Translation of: JavaScript

<lang AppleScript>-- LAST FRIDAYS OF YEAR ------------------------------------------------------

-- lastFridaysOfYear :: Int -> [Date] on lastFridaysOfYear(y)

   -- lastWeekDaysOfYear :: Int -> Int -> [Date]
   script lastWeekDaysOfYear
       on |λ|(intYear, iWeekday)
           
           -- lastWeekDay :: Int -> Int -> Date
           script lastWeekDay
               on |λ|(iLastDay, iMonth)
                   set iYear to intYear
                   
                   calendarDate(iYear, iMonth, iLastDay - ¬
                       (((weekday of calendarDate(iYear, iMonth, iLastDay)) ¬
                           as integer) + (7 - (iWeekday))) mod 7)
               end |λ|
           end script
           
           map(lastWeekDay, lastDaysOfMonths(intYear))
       end |λ|
       
       -- isLeapYear :: Int -> Bool
       on isLeapYear(y)
           (0 = y mod 4) and (0 ≠ y mod 100) or (0 = y mod 400)
       end isLeapYear
       
       -- lastDaysOfMonths :: Int -> [Int]
       on lastDaysOfMonths(y)
           {31, cond(isLeapYear(y), 29, 28), ¬
               31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
       end lastDaysOfMonths
   end script
   
   lastWeekDaysOfYear's |λ|(y, Friday as integer)

end lastFridaysOfYear

-- TEST ---------------------------------------------------------------------- on run argv

   intercalate(linefeed, ¬
       map(isoRow, ¬
           transpose(map(lastFridaysOfYear, ¬
               apply(cond(class of argv is list and argv ≠ {}, ¬
                   singleYearOrRange, fiveCurrentYears), ¬
                   argIntegers(argv))))))

end run

-- ARGUMENT HANDLING ---------------------------------------------------------

-- Up to two optional command line arguments: [yearFrom], [yearTo] -- (Default range in absence of arguments: -- from two years ago, to two years ahead)

-- ~ $ osascript ~/Desktop/lastFridays.scpt -- ~ $ osascript ~/Desktop/lastFridays.scpt 2013 -- ~ $ osascript ~/Desktop/lastFridays.scpt 2013 2016

-- singleYearOrRange :: [Int] -> [Int] on singleYearOrRange(argv)

   apply(cond(length of argv > 0, my enumFromTo, my fiveCurrentYears), argv)

end singleYearOrRange

-- fiveCurrentYears :: () -> [Int] on fiveCurrentYears(_)

   set intThisYear to year of (current date)
   enumFromTo(intThisYear - 2, intThisYear + 2)

end fiveCurrentYears

-- argIntegers :: maybe [String] -> [Int] on argIntegers(argv)

   -- parseInt :: String -> Int
   script parseInt
       on |λ|(s)
           s as integer
       end |λ|
   end script
   
   if class of argv is list and argv ≠ {} then
       {map(parseInt, argv)}
   else
       {}
   end if

end argIntegers

-- GENERIC FUNCTIONS ---------------------------------------------------------

-- Dates and date strings ----------------------------------------------------

-- calendarDate :: Int -> Int -> Int -> Date on calendarDate(intYear, intMonth, intDay)

   tell (current date)
       set {its year, its month, its day, its time} to ¬
           {intYear, intMonth, intDay, 0}
       return it
   end tell

end calendarDate

-- isoDateString :: Date -> String on isoDateString(dte)

   (((year of dte) as string) & ¬
       "-" & text items -2 thru -1 of ¬
       ("0" & ((month of dte) as integer) as string)) & ¬
       "-" & text items -2 thru -1 of ¬
       ("0" & day of dte)

end isoDateString

-- Testing and tabulation ----------------------------------------------------

-- apply (a -> b) -> a -> b on apply(f, a)

   mReturn(f)'s |λ|(a)

end apply

-- cond :: Bool -> (a -> b) -> (a -> b) -> (a -> b) on cond(bool, f, g)

   if bool then
       f
   else
       g
   end if

end cond

-- enumFromTo :: Int -> Int -> [Int] on enumFromTo(m, n)

   if m > n then
       set d to -1
   else
       set d to 1
   end if
   set lst to {}
   repeat with i from m to n by d
       set end of lst to i
   end repeat
   return lst

end enumFromTo

-- intercalate :: Text -> [Text] -> Text on intercalate(strText, lstText)

   set {dlm, my text item delimiters} to ¬
       {my text item delimiters, strText}
   set strJoined to lstText as text
   set my text item delimiters to dlm
   return strJoined

end intercalate

-- isoRow :: [Date] -> String on isoRow(lstDate)

   intercalate(tab, map(my isoDateString, lstDate))

end isoRow

-- map :: (a -> b) -> [a] -> [b] on map(f, xs)

   tell mReturn(f)
       set lng to length of xs
       set lst to {}
       repeat with i from 1 to lng
           set end of lst to |λ|(item i of xs, i, xs)
       end repeat
       return lst
   end tell

end map

-- Lift 2nd class handler function into 1st class script wrapper -- mReturn :: Handler -> Script on mReturn(f)

   if class of f is script then
       f
   else
       script
           property |λ| : f
       end script
   end if

end mReturn

-- transpose :: a -> a on transpose(xss)

   script column
       on |λ|(_, iCol)
           script row
               on |λ|(xs)
                   item iCol of xs
               end |λ|
           end script
           
           map(row, xss)
       end |λ|
   end script
   
   map(column, item 1 of xss)

end transpose</lang>

Output:

2014-01-31    2015-01-30    2016-01-29    2017-01-27    2018-01-26
2014-02-28    2015-02-27    2016-02-26    2017-02-24    2018-02-23
2014-03-28    2015-03-27    2016-03-25    2017-03-31    2018-03-30
2014-04-25    2015-04-24    2016-04-29    2017-04-28    2018-04-27
2014-05-30    2015-05-29    2016-05-27    2017-05-26    2018-05-25
2014-06-27    2015-06-26    2016-06-24    2017-06-30    2018-06-29
2014-07-25    2015-07-31    2016-07-29    2017-07-28    2018-07-27
2014-08-29    2015-08-28    2016-08-26    2017-08-25    2018-08-31
2014-09-26    2015-09-25    2016-09-30    2017-09-29    2018-09-28
2014-10-31    2015-10-30    2016-10-28    2017-10-27    2018-10-26
2014-11-28    2015-11-27    2016-11-25    2017-11-24    2018-11-30
2014-12-26    2015-12-25    2016-12-30    2017-12-29    2018-12-28

A more straightforward solution:

AppleScript's weekday constants can be coerced either to English text or to the integers 1 (for Sunday) to 7 (Saturday).

<lang AppleScript>on lastFridayOfEachMonthInYear(y) -- Initialise an AppleScript date to the first day of some month in the specified year. tell (current date) to set {firstDayOfNextMonth, its day, its year} to {it, 1, y}

-- Get a string representation of y, zero-padded if necessary, and initialise the output string. set y to text 2 thru 5 of ((10000 + y) as text) set outputText to "./last_fridays " & y repeat with nextMonth from 2 to 13 -- Yes! -- For each month in the year, get the first day of the following month. set firstDayOfNextMonth's month to nextMonth -- Calculate the date of the Friday which occurs in the seven days prior to that -- by subtracting a day plus the difference between the previous day's weekday and the target weekday. set lastFridayOfThisMonth to firstDayOfNextMonth - (1 + (firstDayOfNextMonth's weekday) mod 7) * days -- Append the required details to the output text. set {month:m, day:d} to lastFridayOfThisMonth tell (10000 + m * 100 + d) as text to ¬ set outputText to outputText & (linefeed & y & "-" & text 2 thru 3 & "-" & text 4 thru 5) end repeat

return outputText end lastFridayOfEachMonthInYear

lastFridayOfEachMonthInYear(2020)</lang>

Output:

"./last_fridays 2020
2020-01-31
2020-02-28
2020-03-27
2020-04-24
2020-05-29
2020-06-26
2020-07-31
2020-08-28
2020-09-25
2020-10-30
2020-11-27
2020-12-25"

The above is of course hard-coded for Fridays. It can be made more flexible by taking an AppleScript weekday constant as a parameter:

<lang AppleScript>on lastWeekdayWOfEachMonthInYear(w, y) -- Parameters: (AppleScript weekday constant, AD year number) -- Initialise an AppleScript date to the first day of some month in the specified year. tell (current date) to set {firstDayOfNextMonth, its day, its year} to {it, 1, y}

-- Get a string representation of y, zero-padded if necessary, and initialise the output string. set y to text 2 thru 5 of ((10000 + y) as text) set outputText to "./last_" & w & "s " & y repeat with nextMonth from 2 to 13 -- Yes! -- For each month in the year, get the first day of the following month. set firstDayOfNextMonth's month to nextMonth -- Calculate the date of the target weekday which occurs in the seven days prior to that. -- The calculation can be described in various ways, the simplest being the subtraction of a day plus the difference between the previous day's weekday and the target weekday: -- firstDayOfNextMonth - (1 + (((firstDayOfNextMonth's weekday) - 1) - w + 7) mod 7) * days -- But they all boil down to: set lastWOfThisMonth to firstDayOfNextMonth - (1 + ((firstDayOfNextMonth's weekday) - w + 6) mod 7) * days -- Get the day and month of the calculated date and append the required details to the output text. set {month:m, day:d} to lastWOfThisMonth tell (10000 + m * 100 + d) as text to ¬ set outputText to outputText & (linefeed & y & "-" & text 2 thru 3 & "-" & text 4 thru 5) end repeat

return outputText end lastWeekdayWOfEachMonthInYear

lastWeekdayWOfEachMonthInYear(Friday, 2020)</lang>

Output:

"./last_Fridays 2020
2020-01-31
2020-02-28
2020-03-27
2020-04-24
2020-05-29
2020-06-26
2020-07-31
2020-08-28
2020-09-25
2020-10-30
2020-11-27
2020-12-25"

Arturo

<lang rebol>lastFridayForMonth: function [m][

   ensure -> in? m 1..12

   daysOfMonth: [0 31 27 31 30 31 30 31 31 30 31 30 31]
   loop range get daysOfMonth m 1 [d][
       dt: to :date.format:"yyyy-M-dd" ~"2012-|m|-|d|"
       if dt\Day = "Friday" -> return dt
   ]

]

loop 1..12 'month [

   print to :string.format:"yyyy-MM-dd" lastFridayForMonth month

]</lang>

Output:

AutoHotkey

<lang AHK>if 1 = ; no parameter passed { InputBox, 1, Last Fridays of year, Enter a year:, , , , , , , , %A_YYYY% If ErrorLevel ExitApp }

YYYY = %1% ; retrieve command line parameter Stmp = %YYYY%0101000000 count= 0

While count < 12 { FormatTime, ddd, %stmp%, ddd FormatTime, M, %stmp%, M If (ddd = "Fri"){ if (M-1 = count){ t := stmp stmp += 7, days } else res .= SubStr(t, 1, 4) "-" SubStr(t, 5, 2) "-" SubStr(t, 7, 2) "`n" ,count++ ,stmp := YYYY . SubStr("0" M, -1) . "01" } else stmp += 1, days } MsgBox % res</lang>

Output:

for 2012

AutoIt

include <Date.au3>

$iYear = InputBox('Last Friday in each month', 'Please input the year:')

_GetLastFridays($iYear)

Func _GetLastFridays($_iYear) Local $sResult = 'last fridays in ' & $_iYear & @LF, $iDay Local $aDaysInMonth[12] = [31,28,31,30,31,30,31,31,30,31,30,31] If _DateIsLeapYear($_iYear) Then $aDaysInMonth[1] = 29 For $i = 1 To 12 $iDay = $aDaysInMonth[$i-1] While 1 If _DateToDayOfWeekISO($_iYear, $i, $iDay) = 5 Then $sResult &= StringFormat('%4d-%02d-%02d', $_iYear, $i, $iDay) & @LF ExitLoop EndIf $iDay -= 1 WEnd Next ConsoleWrite($sResult) EndFunc ;==>_GetFridays </lang>

Output:

last fridays in 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

--BugFix (talk) 13:27, 15 November 2013 (UTC)

AWK

syntax: GAWK -f LAST_FRIDAY_OF_EACH_MONTH.AWK year
converted from Fortran

BEGIN {

   split("31,28,31,30,31,30,31,31,30,31,30,31",daynum_array,",") # days per month in non leap year
   year = ARGV[1]
   if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)) {
     daynum_array[2] = 29
   }
   y = year - 1
   k = 44 + y + int(y/4) + int(6*(y/100)) + int(y/400)
   for (m=1; m<=12; m++) {
     k += daynum_array[m]
     d = daynum_array[m] - (k%7)
     printf("%04d-%02d-%02d\n",year,m,d)
   }
   exit(0)

} </lang>

Output:

Befunge

Translation of: C

The algorithm has been slightly simplified to avoid the additional day adjustment inside the loop, and the year is obtained from stdin rather than via the command line.

Output:

Year:2012

2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

C

Doesn't work with Julian calendar (then again, you probably don't need to plan your weekends for middle ages).

<lang c>#include <stdio.h>

include <stdlib.h>

int main(int c, char *v[]) { int days[] = {31,29,31,30,31,30,31,31,30,31,30,31}; int m, y, w;

if (c < 2 || (y = atoi(v[1])) <= 1700) return 1;

	days[1] -= (y % 4) || (!(y % 100) && (y % 400));

w = y * 365 + (y - 1) / 4 - (y - 1) / 100 + (y - 1) / 400 + 6;

for(m = 0; m < 12; m++) { w = (w + days[m]) % 7; printf("%d-%02d-%d\n", y, m + 1, days[m] + (w < 5 ? -2 : 5) - w); }

return 0; }</lang>

C#

<lang csharp>using System; using System.Collections.Generic; using System.Globalization; using System.Linq;

namespace RosettaCode.LastFridaysOfYear {

   internal static class Program
   {
       private static IEnumerable<DateTime> LastFridaysOfYear(int year)
       {
           for (var month = 1; month <= 12; month++)
           {
               var date = new DateTime(year, month, 1).AddMonths(1).AddDays(-1);
               while (date.DayOfWeek != DayOfWeek.Friday)
               {
                   date = date.AddDays(-1);
               }
               yield return date;
           }
       }

       private static void Main(string[] arguments)
       {
           int year;
           var argument = arguments.FirstOrDefault();
           if (string.IsNullOrEmpty(argument) || !int.TryParse(argument, out year))
           {
               year = DateTime.Today.Year;
           }

           foreach (var date in LastFridaysOfYear(year))
           {
               Console.WriteLine(date.ToString("d", CultureInfo.InvariantCulture));
           }
       }
   }

}</lang>

Output:

C++

Library: Boost

called with ./last_fridays 2012 <lang cpp>#include <boost/date_time/gregorian/gregorian.hpp>

include <iostream>
include <cstdlib>

int main( int argc , char* argv[ ] ) {

  using namespace boost::gregorian ;

  greg_month months[ ] = { Jan , Feb , Mar , Apr , May , Jun , Jul ,
     Aug , Sep , Oct , Nov , Dec } ;
  greg_year gy = atoi( argv[ 1 ] ) ;
  for ( int i = 0 ; i < 12 ; i++ ) {
     last_day_of_the_week_in_month lwdm ( Friday , months[ i ] ) ;
     date d = lwdm.get_date( gy ) ;
     std::cout << d << std::endl ;
  }
  return 0 ;

}</lang>

Output:

2012-Jan-27
2012-Feb-24
2012-Mar-30
2012-Apr-27
2012-May-25
2012-Jun-29
2012-Jul-27
2012-Aug-31
2012-Sep-28
2012-Oct-26
2012-Nov-30
2012-Dec-28

Clojure

Library: clj-time

<lang clojure>(use '[clj-time.core :only [last-day-of-the-month day-of-week minus days]]

    '[clj-time.format :only [unparse formatters]])

(defn last-fridays [year]

 (let [last-days (map #(last-day-of-the-month year %) (range 1 13 1)) 
       dow (map day-of-week last-days) 
       relation (zipmap last-days dow)] 
   (map #(minus (key %) (days (mod (+ (val %) 2) 7))) relation)))

(defn last-fridays-formatted [year]

 (sort (map #(unparse (formatters :year-month-day) %) (last-fridays year))))</lang>

Output:

user=> (pprint (last-fridays-formatted 2012))
("2012-01-27"
 "2012-02-24"
 "2012-03-30"
 "2012-04-27"
 "2012-05-25"
 "2012-06-29"
 "2012-07-27"
 "2012-08-31"
 "2012-09-28"
 "2012-10-26"
 "2012-11-30"
 "2012-12-28")

COBOL

      program-id. last-fri.
      data division.
      working-storage section.
      1 wk-date.
       2 yr pic 9999.
       2 mo pic 99 value 1.
       2 da pic 99 value 1.
      1 rd-date redefines wk-date pic 9(8).
      1 binary.
       2 int-date pic 9(8).
       2 dow pic 9(4).
       2 friday pic 9(4) value 5.
      procedure division.
          display "Enter a calendar year (1601 thru 9999): "
              with no advancing
          accept yr
          if yr >= 1601 and <= 9999
              continue
          else
              display "Invalid year"
              stop run
          end-if
          perform 12 times
              move 1 to da
              add 1 to mo
              if mo > 12              *> to avoid y10k in 9999
                  move 12 to mo
                  move 31 to da
              end-if
              compute int-date = function
                  integer-of-date (rd-date)
              if mo =12 and da = 31   *> to avoid y10k in 9999
                  continue
              else
                  subtract 1 from int-date
              end-if
              compute rd-date = function
                  date-of-integer (int-date)
              compute dow = function mod
                  ((int-date - 1) 7) + 1
              compute dow = function mod ((dow - friday) 7)
              subtract dow from da
              display yr "-" mo "-" da
              add 1 to mo
          end-perform
          stop run
          .
      end program last-fri.

</lang>

Output:

CoffeeScript

<lang coffeescript> last_friday_of_month = (year, month) ->

 # month is 1-based, JS API is 0-based, then we use
 # non-positive indexes to work backward relative to the
 # first day of the next month
 i = 0
 while true
   last_day = new Date(year, month, i) 
   if last_day.getDay() == 5
     return last_day.toDateString()
   i -= 1

print_last_fridays_of_month = (year) ->

 for month in [1..12]
   console.log last_friday_of_month year, month

do ->

 year = parseInt process.argv[2]
 print_last_fridays_of_month year

</lang>

Output:

<lang> > coffee last_friday.coffee 2012 Fri Jan 27 2012 Fri Feb 24 2012 Fri Mar 30 2012 Fri Apr 27 2012 Fri May 25 2012 Fri Jun 29 2012 Fri Jul 27 2012 Fri Aug 31 2012 Fri Sep 28 2012 Fri Oct 26 2012 Fri Nov 30 2012 Fri Dec 28 2012 </lang>

Common Lisp

Works with: CLISP

The command-line argument processing is the only CLISP-specific code.

<lang lisp>(defun friday-before (year month day)

(let* 
 ((timestamp (encode-universal-time 0 0 12 day month year))
  (weekday (nth 6 (multiple-value-list (decode-universal-time timestamp))))
  (fri (- timestamp (* (+ (mod (+ weekday 2) 7) 1) 86400))))
   (multiple-value-bind (_ _ _ d m y) (decode-universal-time fri)
    (list y m d))))

(defun last-fridays (year)

 (append (loop for month from 2 to 12 collecting (friday-before year month 1))
         (list (friday-before (1+ year) 1 1))))

(let* ((year (read-from-string (car *args*))))

 (format t "~{~{~a-~2,'0d-~2,'0d~}~%~}" (last-fridays year)))</lang>

Sample run for the year 2015:

Output:

D

<lang d>import std.stdio, std.datetime, std.traits;

void lastFridays(in uint year) {

   auto date = Date(year, 1, 1);
   foreach (_; [EnumMembers!Month]) {
       date.day(date.daysInMonth);
       date.roll!"days"(-(date.dayOfWeek + 2) % 7);
       writeln(date);
       date.add!"months"(1, AllowDayOverflow.no);
   }

}

void main() {

   lastFridays(2012);

}</lang>

2012-Jan-27
2012-Feb-24
2012-Mar-30
2012-Apr-27
2012-May-25
2012-Jun-29
2012-Jul-27
2012-Aug-31
2012-Sep-28
2012-Oct-26
2012-Nov-30
2012-Dec-28

Delphi

Uses the standard Delphi library. <lang delphi>program LastFridayOfMonth;

{$APPTYPE CONSOLE}

uses

 System.SysUtils, System.DateUtils;

var

 Year: Word;
 Month: Word;
 D1: TDateTime;
 D2: Word;

begin

 Write('Enter year: ');
 ReadLn(Year);

 for Month := MonthJanuary to MonthDecember do begin
   D1 := EndOfAMonth(Year, Month);
   D2 := DayOfTheWeek(D1);
   while D2 <> DayFriday do begin
     D1 := IncDay(D1, -1);
     D2 := DayOfTheWeek(D1);
   end;
   WriteLn(DateToStr(D1));
 end;

end.</lang>

Output:

Enter year: 2019
25.01.2019
22.02.2019
29.03.2019
26.04.2019
31.05.2019
28.06.2019
26.07.2019
30.08.2019
27.09.2019
25.10.2019
29.11.2019
27.12.2019

Elixir

<lang elixir>defmodule RC do

 def lastFriday(year) do
   Enum.map(1..12, fn month ->
     lastday = :calendar.last_day_of_the_month(year, month)
     daynum = :calendar.day_of_the_week(year, month, lastday)
     friday = lastday - rem(daynum + 2, 7)
     {year, month, friday}
   end)
 end

end

y = String.to_integer(hd(System.argv)) Enum.each(RC.lastFriday(y), fn {year, month, day} ->

 :io.format "~4b-~2..0w-~2..0w~n", [year, month, day]

end)</lang>

Output:

Elm

<lang elm>import Html exposing (Html, Attribute, text, div, input) import Html.App exposing (beginnerProgram) import Html.Attributes exposing (placeholder, value, style) import Html.Events exposing (onInput) import String exposing (toInt) import Maybe exposing (withDefault) import List exposing (map, map2) import List.Extra exposing (scanl1)

type Msg = SetYear String

lastFridays : Int -> List Int lastFridays year =

 let isLeap = (year % 400) == 0 || ( (year % 4) == 0 && (year % 100) /= 0 )
     daysInMonth = [31, if isLeap then 29 else 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
     y = year-1
 in scanl1 (+) daysInMonth
    |> map2 (\len day -> len - (day + 2 + y + y//4 - y//100 + y//400) % 7) daysInMonth

lastFridayStrings : String -> List String lastFridayStrings yearString =

 let months= ["January ", "February ", "March ", "April ", "May ", "June ", "July ", "August ", "September ", "October ", "November ", "December "]
     errString = "Only years after 1752 are valid."
 in case toInt yearString of 
      Ok year -> 
          if (year < 1753) 
          then [errString] 
          else lastFridays year
               |> map2 (\m d -> m ++ toString d ++ ", " ++ toString year) months
      Err _ -> 
          [errString]

view : String -> Html Msg view yearString =

 div []
   ([ input
       [ placeholder "Enter a year."
       , value yearString
       , onInput SetYear
       , myStyle
       ]
       []
    ] ++ (lastFridayStrings yearString
          |> map (\date -> div [ myStyle ] [ text date ]) ))

myStyle : Attribute Msg myStyle =

 style
   [ ("width", "100%")
   , ("height", "20px")
   , ("padding", "5px 0 0 5px")
   , ("font-size", "1em")
   , ("text-align", "left")
   ]

update : Msg -> String -> String update msg _ =

   case msg of
       SetYear yearString -> yearString

main =

   beginnerProgram
       { model = ""
       , view = view
       , update = update
       }</lang>

Link to live demo: http://dc25.github.io/lastFridayOfMonthElm/

Sample run for the year 2003; copied and pasted from web-page:

Output:

January 31, 2003
February 28, 2003
March 28, 2003
April 25, 2003
May 30, 2003
June 27, 2003
July 25, 2003
August 29, 2003
September 26, 2003
October 31, 2003
November 28, 2003
December 26, 2003

Erlang

<lang Erlang> -module( last_date_each_month ).

-export( [monday/1, tuesday/1, wednesday/1, thursday/1, friday/1, saturday/1, sunday/1] ).

monday( Year ) -> last( Year, 1 ). tuesday( Year ) -> last( Year, 2 ). wednesday( Year ) -> last( Year, 3 ). thursday( Year ) -> last( Year, 4 ). friday( Year ) -> last( Year, 5 ). saturday( Year ) -> last( Year, 6 ). sunday( Year ) -> last( Year, 7 ).

last( Year, Week_day ) ->

   Months = lists:seq( 1, 12 ),
   Months_days = [{X, Y} || X <- Months, Y <- lists:seq(calendar:last_day_of_the_month(Year, X), calendar:last_day_of_the_month(Year, X) - 7, -1), calendar:valid_date(Year, X, Y), calendar:day_of_the_week(Year, X, Y) =:= Week_day],
   [{Year, X, proplists:get_value(X, Months_days)} || X <- Months].

</lang>

Output:

32> [io:fwrite("~B-~2.10.0B-~B~n", [Y,M,D]) || {Y,M,D} <- last_date_each_month:friday(2012)].
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Factor

Works with: Factor version 0.98

The last-friday-of-month word in the calendar vocabulary does most of the work. This program expects the year as a command line argument. <lang factor>USING: calendar calendar.format command-line io kernel math.parser sequences ; IN: rosetta-code.last-fridays

(command-line) second string>number <year> 12 <iota> [ months time+ last-friday-of-month ] with map [ timestamp>ymd print ] each</lang>

Output:

>factor last-fridays.factor 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Fortran

Algorithm: compute day of week for last day of month, then subtract just enough to get to the preceding friday. Do this for each month. To simplify computations further, we only need to compute day of week of january 1st (the others are found by adding month lengths). Since day of week need only be known modulo 7, we do not compute modulo at all except once when subtracting. <lang fortran>program fridays

  implicit none
  integer :: days(1:12) = (/31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31/)
  integer :: year, k, y, m
  read *, year
  if (mod(year, 400) == 0 .or. (mod(year, 4) == 0 .and. mod(year, 100) /= 0)) days(2) = 29
  y = year - 1
  k = 44 + y + y/4 + 6*(y/100) + y/400
  do m = 1, 12
     k = k + days(m)
     print "(I4,A1,I2.2,A1,I2)", year, '-', m, '-', days(m) - mod(k, 7)
  end do

end program </lang>

FreeBASIC

<lang FreeBasic>' version 23-06-2015 ' compile with: fbc -s console

Ifndef TRUE ' define true and false for older freebasic versions

   #Define FALSE 0
   #Define TRUE Not FALSE

EndIf

Function leapyear(Year_ As Integer) As Integer

   ' from the leapyear entry
   If (Year_ Mod 4) <> 0 Then Return FALSE
   If (Year_ Mod 100) = 0 AndAlso (Year_ Mod 400) <> 0 Then Return FALSE
   Return TRUE

End Function

Function wd(m As Integer, d As Integer, y As Integer) As Integer

   ' Zellerish
   ' 0 = Sunday, 1 = Monday, 2 = Tuesday, 3 = Wednesday
   ' 4 = Thursday, 5 = Friday, 6 = Saturday

   If m < 3 Then        ' If m = 1 Or m = 2 Then
       m += 12
       y -= 1
   End If
   Return (y + (y \ 4) - (y \ 100) + (y \ 400) + d + ((153 * m + 8) \ 5)) Mod 7

End Function

' ------=< MAIN >=------

Type month_days

   m_name As String
   days As UByte

End Type

Dim As month_days arr(1 To 12) Data "January", 31, "February", 28, "March", 31, "April", 30 Data "May", 31, "June", 30, "July", 31, "August", 31 Data "September", 30, "October", 31, "November", 30, "December", 31

Dim As Integer yr, d, i, x Dim As String keypress

For i = 1 To 12

   With arr(i)
       Read .m_name
       Read .days
   End With

   Do
       Print "For what year do you want to find the last Friday of the month"
       Input "any number below 1800 stops program, year in YYYY format";yr
       ' empty input also stops
       If yr < 1800 Then
           End
       Else
           Exit Do
       End If
   Loop

   Print : Print
   Print "Last Friday of the month for"; yr

   For i = 1 To 12
       d = arr(i).days
       If i = 2 AndAlso leapyear(yr) = TRUE Then d = d + 1
       x = wd(i, d, yr)
       If x <> 5 Then d = d - IIf(x > 5, x - 5, x + 2)
       Print d; " "; arr(i).m_name
   Next

   ' empty key buffer
   While InKey <> "" : keypress = InKey : Wend
   Print : Print
   Print "Find last Friday for a other year [Y|y], anything else stops"
   keypress =""
   While keypress = "" : keypress = InKey : Wend
   If LCase(keypress) <> "y" Then Exit Do
   Print : Print

Loop End</lang>

Output:

For what year do you want to find the last Friday of the month
any number below 1800 stops program, year in YYYY format? 2017

Last Friday of the month for 2017
 27 January
 24 February
 31 March
 28 April
 26 May
 30 June
 28 July
 25 August
 29 September
 27 October
 24 November
 29 December

Frink

<lang frink>d = parseDate[ARGS@0] for m = 1 to 12 {

  d = beginningOfNextMonth[d]
  n = d - (((parseInt[d -> ### u ###] + 1) mod 7) + 1) days
  println[n->###yyyy-MM-dd###]

}</lang>

Output:

Fōrmulæ

Fōrmulæ programs are not textual, visualization/edition of programs is done showing/manipulating structures but not text. Moreover, there can be multiple visual representations of the same program. Even though it is possible to have textual representation —i.e. XML, JSON— they are intended for storage and transfer purposes more than visualization and edition.

Programs in Fōrmulæ are created/edited online in its website, However they run on execution servers. By default remote servers are used, but they are limited in memory and processing power, since they are intended for demonstration and casual use. A local server can be downloaded and installed, it has no limitations (it runs in your own computer). Because of that, example programs can be fully visualized and edited, but some of them will not run if they require a moderate or heavy computation/memory resources, and no local server is being used.

In this page you can see the program(s) related to this task and their results.

Gambas

<lang gambas>Public Sub Form_Open() Dim siYear As Short = InputBox("Please input a year", "Last Friday of each month") Dim siMonth, siDay As Short Dim dDay As Date

For siMonth = 1 To 12

 For siDay = 31 DownTo 22
   Try dDay = Date(siYear, siMonth, siDay)
   If Error Then Continue
   If WeekDay(dDay) = 5 Then 
     Print Format(dDay, "yyyy-mm-dd");;
     Print Space(6) & Format(dDay, "dddd dd mmmm yyyy")
     Break
   End If
 Next

End</lang> Output:

1925-01-30       Friday 30 January 1925
1925-02-27       Friday 27 February 1925
1925-03-27       Friday 27 March 1925
1925-04-24       Friday 24 April 1925
1925-05-29       Friday 29 May 1925
1925-06-26       Friday 26 June 1925
1925-07-31       Friday 31 July 1925
1925-08-28       Friday 28 August 1925
1925-09-25       Friday 25 September 1925
1925-10-30       Friday 30 October 1925
1925-11-27       Friday 27 November 1925
1925-12-25       Friday 25 December 1925

Go

<lang go>package main

import ( "fmt" "os" "strconv" "time" )

func main() { y := time.Now().Year() if len(os.Args) == 2 { if i, err := strconv.Atoi(os.Args[1]); err == nil { y = i } } for m := time.January; m <= time.December; m++ { d := time.Date(y, m+1, 1, 0, 0, 0, 0, time.UTC).Add(-24 * time.Hour) d = d.Add(-time.Duration((d.Weekday()+7-time.Friday)%7) * 24 * time.Hour) fmt.Println(d.Format("2006-01-02")) } }</lang>

Output:

> ./fridays 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Groovy

Solution: Same as Find last Sunday of each month

Test: <lang groovy>def ymd = { it.format('yyyy-MM-dd') } def lastFridays = lastWeekDays.curry(Day.Fri) lastFridays(args[0] as int).each { println (ymd(it)) }</lang>

Execution (Cygwin on Windows 7):

[2273] groovy lastFridays.groovy 2012

Output:

Haskell

<lang Haskell>import Data.Time.Calendar

      (Day, addDays, showGregorian, fromGregorian, gregorianMonthLength)

import Data.Time.Calendar.WeekDate (toWeekDate) import Data.List (transpose, intercalate)

-- [1 .. 7] for [Mon .. Sun] findWeekDay :: Int -> Day -> Day findWeekDay dayOfWeek date =

 head
   (filter
      (\x ->
          let (_, _, day) = toWeekDate x
          in day == dayOfWeek)
      ((`addDays` date) <$> [-6 .. 0]))

weekDayDates :: Int -> Integer -> [String] weekDayDates dayOfWeek year =

 ((showGregorian . findWeekDay dayOfWeek) .
  (fromGregorian year <*> gregorianMonthLength year)) <$>
 [1 .. 12]

main :: IO () main =

 mapM_
   putStrLn
   (intercalate "  " <$> transpose (weekDayDates 5 <$> [2012 .. 2017]))</lang>

Output:

2012-01-27  2013-01-25  2014-01-31  2015-01-30  2016-01-29  2017-01-27
2012-02-24  2013-02-22  2014-02-28  2015-02-27  2016-02-26  2017-02-24
2012-03-30  2013-03-29  2014-03-28  2015-03-27  2016-03-25  2017-03-31
2012-04-27  2013-04-26  2014-04-25  2015-04-24  2016-04-29  2017-04-28
2012-05-25  2013-05-31  2014-05-30  2015-05-29  2016-05-27  2017-05-26
2012-06-29  2013-06-28  2014-06-27  2015-06-26  2016-06-24  2017-06-30
2012-07-27  2013-07-26  2014-07-25  2015-07-31  2016-07-29  2017-07-28
2012-08-31  2013-08-30  2014-08-29  2015-08-28  2016-08-26  2017-08-25
2012-09-28  2013-09-27  2014-09-26  2015-09-25  2016-09-30  2017-09-29
2012-10-26  2013-10-25  2014-10-31  2015-10-30  2016-10-28  2017-10-27
2012-11-30  2013-11-29  2014-11-28  2015-11-27  2016-11-25  2017-11-24
2012-12-28  2013-12-27  2014-12-26  2015-12-25  2016-12-30  2017-12-29

Icon and Unicon

This will write the last fridays for every year given as an argument. There is no error checking on the year. <lang Icon>procedure main(A) every write(lastfridays(!A)) end

procedure lastfridays(year) every m := 1 to 12 do {

  d := case m of {
     2        : if IsLeapYear(year) then 29 else 28
     4|6|9|11 : 30
     default  : 31
     }                          # last day of month
      
  z := 0  
  j := julian(m,d,year) + 1     # first day of next month
  until (j-:=1)%7 = 4 do z -:=1 # backup to last friday=4
  suspend sprintf("%d-%d-%d",year,m,d+z)
  }

end

link datetime, printf</lang>

Library: Icon Programming Library

printf.icn provides formatting datetime.icn provides julian and IsLeapYear

Output:

last_fridays.exe 2012
2012-1-27
2012-2-24
2012-3-30
2012-4-27
2012-5-25
2012-6-29
2012-7-27
2012-8-31
2012-9-28
2012-10-26
2012-11-30
2012-12-28

J

<lang j>require 'dates' last_fridays=: 12 {. [: ({:/.~ }:"1)@(#~ 5 = weekday)@todate (i.366) + todayno@,&1 1</lang>

In other words, start from January 1 of the given year, and count forward for 366 days, keeping the Fridays. Then pick the last remaining day within each represented month (which will be a Friday because we only kept the Fridays). Then pick the first 12 (since on a non-leap year which ends on a Thursday we would get an extra Friday).

Example use:

<lang j> last_fridays 2012 2012 1 27 2012 2 24 2012 3 30 2012 4 27 2012 5 25 2012 6 29 2012 7 27 2012 8 31 2012 9 28 2012 10 26 2012 11 30 2012 12 28</lang>

Java

Works with: Java version 1.5+

<lang java5>import java.text.*; import java.util.*;

public class LastFridays {

   public static void main(String[] args) throws Exception {
       int year = Integer.parseInt(args[0]);
       GregorianCalendar c = new GregorianCalendar(year, 0, 1);

       for (String mon : new DateFormatSymbols(Locale.US).getShortMonths()) {
           if (!mon.isEmpty()) {
               int totalDaysOfMonth = c.getActualMaximum(Calendar.DAY_OF_MONTH);
               c.set(Calendar.DAY_OF_MONTH, totalDaysOfMonth);

               int daysToRollBack = (c.get(Calendar.DAY_OF_WEEK) + 1) % 7;

               int day = totalDaysOfMonth - daysToRollBack;
               c.set(Calendar.DAY_OF_MONTH, day);

               System.out.printf("%d %s %d\n", year, mon, day);

               c.set(year, c.get(Calendar.MONTH) + 1, 1);
           }
       }
   }

}</lang>

Output:

(for java LastFridays 2012)

2012 Jan 27
2012 Feb 24
2012 Mar 30
2012 Apr 27
2012 May 25
2012 Jun 29
2012 Jul 27
2012 Aug 31
2012 Sep 28
2012 Oct 26
2012 Nov 30
2012 Dec 28

JavaScript

ES5

Iteration

Works with: Nodejs

<lang javascript>var last_friday_of_month, print_last_fridays_of_month;

last_friday_of_month = function(year, month) {

 var i, last_day;
 i = 0;
 while (true) {
   last_day = new Date(year, month, i);
   if (last_day.getDay() === 5) {
     return last_day.toDateString();
   }
   i -= 1;
 }

};

print_last_fridays_of_month = function(year) {

 var month, results;
 results = [];
 for (month = 1; month <= 12; ++month) {
   results.push(console.log(last_friday_of_month(year, month)));
 }
 return results;

};

(function() {

 var year;
 year = parseInt(process.argv[2]);
 return print_last_fridays_of_month(year);

})();</lang>

Output:

>node lastfriday.js  2015
Fri Jan 30 2015
Fri Feb 27 2015
Fri Mar 27 2015
Fri Apr 24 2015
Fri May 29 2015
Fri Jun 26 2015
Fri Jul 31 2015
Fri Aug 28 2015
Fri Sep 25 2015
Fri Oct 30 2015
Fri Nov 27 2015
Fri Dec 25 2015

Functional composition

<lang JavaScript>(function () {

   'use strict';

   // lastFridaysOfYear :: Int -> [Date]
   function lastFridaysOfYear(y) {
       return lastWeekDaysOfYear(y, days.friday);
   }

   // lastWeekDaysOfYear :: Int -> Int -> [Date]
   function lastWeekDaysOfYear(y, iWeekDay) {
       return [
               31,
               0 === y % 4 && 0 !== y % 100 || 0 === y % 400 ? 29 : 28,
               31, 30, 31, 30, 31, 31, 30, 31, 30, 31
           ]
           .map(function (d, m) {
               var dte = new Date(Date.UTC(y, m, d));

               return new Date(Date.UTC(
                   y, m, d - (
                       (dte.getDay() + (7 - iWeekDay)) % 7
                   )
               ));
           });
   }

   // isoDateString :: Date -> String
   function isoDateString(dte) {
       return dte.toISOString()
           .substr(0, 10);
   }

   // range :: Int -> Int -> [Int]
   function range(m, n) {
       return Array.apply(null, Array(n - m + 1))
           .map(function (x, i) {
               return m + i;
           });
   }

   // transpose :: a -> a
   function transpose(lst) {
       return lst[0].map(function (_, iCol) {
           return lst.map(function (row) {
               return row[iCol];
           });
       });
   }

   var days = {
       sunday: 0,
       monday: 1,
       tuesday: 2,
       wednesday: 3,
       thursday: 4,
       friday: 5,
       saturday: 6
   }

   // TEST
   return transpose(
           range(2012, 2016)
           .map(lastFridaysOfYear)
       )
       .map(function (row) {
           return row
               .map(isoDateString)
               .join('\t');
       })
       .join('\n');

})();</lang>

Output:

2012-01-27	2013-01-25	2014-01-31	2015-01-30	2016-01-29
2012-02-24	2013-02-22	2014-02-28	2015-02-27	2016-02-26
2012-03-30	2013-03-29	2014-03-28	2015-03-27	2016-03-25
2012-04-27	2013-04-26	2014-04-25	2015-04-24	2016-04-29
2012-05-25	2013-05-31	2014-05-30	2015-05-29	2016-05-27
2012-06-29	2013-06-28	2014-06-27	2015-06-26	2016-06-24
2012-07-27	2013-07-26	2014-07-25	2015-07-31	2016-07-29
2012-08-31	2013-08-30	2014-08-29	2015-08-28	2016-08-26
2012-09-28	2013-09-27	2014-09-26	2015-09-25	2016-09-30
2012-10-26	2013-10-25	2014-10-31	2015-10-30	2016-10-28
2012-11-30	2013-11-29	2014-11-28	2015-11-27	2016-11-25
2012-12-28	2013-12-27	2014-12-26	2015-12-25	2016-12-30

ES6

<lang JavaScript>(() => {

   'use strict'

   // lastWeekDaysOfYear :: Int -> Int -> [Date]
   const lastWeekDaysOfYear = (iWeekDay, y) => [
           31,
           0 === y % 4 && 0 !== y % 100 || 0 === y % 400 ? 29 : 28,
           31, 30, 31, 30, 31, 31, 30, 31, 30, 31
       ]
       .map((d, m) =>
           new Date(Date.UTC(
               y, m, d - ((new Date(Date.UTC(y, m, d))
                   .getDay() + (7 - iWeekDay)) % 7))));

   const days = {
       sunday: 0,
       monday: 1,
       tuesday: 2,
       wednesday: 3,
       thursday: 4,
       friday: 5,
       saturday: 6
   };

   // GENERIC FUNCTIONS

   // curry :: ((a, b) -> c) -> a -> b -> c
   const curry = f => a => b => f(a, b);

   // isoDateString :: Date -> String
   const isoDateString = dte =>
       dte.toISOString()
       .substr(0, 10);

   // range :: Int -> Int -> [Int]
   const range = (m, n) =>
       Array.from({
           length: Math.floor(n - m) + 1
       }, (_, i) => m + i);

   // transpose :: a -> a
   const transpose = lst =>
       lst[0].map((_, iCol) =>
           lst.map(row => row[iCol]));

   // TEST
   return transpose(
           range(2015, 2019)
           .map(curry(lastWeekDaysOfYear)(days.friday))
       )
       .map(row => row
           .map(isoDateString)
           .join('\t'))
       .join('\n');

})();</lang>

Output:

2015-01-30    2016-01-29    2017-01-27    2018-01-26    2019-01-25
2015-02-27    2016-02-26    2017-02-24    2018-02-23    2019-02-22
2015-03-27    2016-03-25    2017-03-31    2018-03-30    2019-03-29
2015-04-24    2016-04-29    2017-04-28    2018-04-27    2019-04-26
2015-05-29    2016-05-27    2017-05-26    2018-05-25    2019-05-31
2015-06-26    2016-06-24    2017-06-30    2018-06-29    2019-06-28
2015-07-31    2016-07-29    2017-07-28    2018-07-27    2019-07-26
2015-08-28    2016-08-26    2017-08-25    2018-08-31    2019-08-30
2015-09-25    2016-09-30    2017-09-29    2018-09-28    2019-09-27
2015-10-30    2016-10-28    2017-10-27    2018-10-26    2019-10-25
2015-11-27    2016-11-25    2017-11-24    2018-11-30    2019-11-29
2015-12-25    2016-12-30    2017-12-29    2018-12-28    2019-12-27

jq

Works with: jq version 1.4

Foundations <lang jq># In case your jq does not have "until" defined:

def until(cond; next):

 def _until:
   if cond then . else (next|_until) end;
 _until;

Zeller's Congruence is from Day_of_the_week#jq

Use Zeller's Congruence to determine the day of the week, given
year, month and day as integers in the conventional way.
If iso == "iso" or "ISO", then emit an integer in 1 -- 7 where
1 represents Monday, 2 Tuesday, etc;
otherwise emit 0 for Saturday, 1 for Sunday, etc.

def day_of_week(year; month; day; iso):

 if month == 1 or month == 2 then
   [year - 1, month + 12, day]
 else
   [year, month, day]
 end
 | .[2] + (13*(.[1] + 1)/5|floor) 
   +  (.[0]%100)       + ((.[0]%100)/4|floor)
   +  (.[0]/400|floor) - 2*(.[0]/100|floor)
 | if iso == "iso" or iso == "ISO" then 1 + ((. + 5) % 7)
   else . % 7
   end ;</lang>

findLastFridays <lang jq># year and month are numbered conventionally def findLastFriday(year; month):

 def isLeapYear:
   year%4 == 0 and ( year%100!=0 or year%400==0 ) ;
 def days:
   if month == 2 then (if isLeapYear then 29 else 28 end)
   else [31, 28, 31,30,31,30,31,31,30,31,30,31][month-1]
   end;
 year as $year
 | month as $month
 | days
 | until( day_of_week($year; $month; .; null) == 6 ; .-1);

input: year

def findLastFridays:

 def months:
   ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
 . as $year
 | "YEAR: \(.)",
   (range(0;12) | "\(months[.]) \(findLastFriday($year; .+1))") ;

$year|tonumber|findLastFridays</lang>

Output:

<lang sh>$ jq --arg year 2012 -n -r -f findLastFridays.jq YEAR: 2012 January 27 February 24 March 30 April 27 May 25 June 29 July 27 August 31 September 28 October 26 November 30 December 28</lang>

Julia

<lang Julia>using Dates

const wday = Dates.Fri const lo = 1 const hi = 12

print("\nThis script will print the last ", Dates.dayname(wday)) println("s of each month of the year given.") println("(Leave input empty to quit.)")

while true

   print("\nYear> ")
   y = chomp(readline())
   0 < length(y) || break
   y = try
       parseint(y)
   catch
       println("Sorry, but \"", y, "\" does not compute as a year.")
       continue
   end
   println()
   for m in Date(y, lo):Month(1):Date(y, hi)
       println("    ", tolast(m, wday))
   end

end

</lang>

Output:

This script will print the last Fridays of each month of the year given.
(Leave input empty to quit.)

Year> 2012

    2012-01-27
    2012-02-24
    2012-03-30
    2012-04-27
    2012-05-25
    2012-06-29
    2012-07-27
    2012-08-31
    2012-09-28
    2012-10-26
    2012-11-30
    2012-12-28

Year> this year 
Sorry, but "this year" does not compute as a year.

Year>

K

<lang K> / List the dates of last Fridays of each month of / a given year / lastfridt.k

isleap: {(+/~x!' 4 100 400)!2} wd: {(_jd x)!7} dom: (31;28;31;30;31;30;31;31;30;31;30;31) init: {:[isleap x;dom[1]::29;dom[1]::28]} wdme: {[m;y]; init y; dt:(10000*y)+(100*m)+dom[m-1];jd::(_jd dt);mewd::(wd dt)} lfd: {[m;y]; wdme[m;y];:[mewd>3;jd::jd+(4-mewd);jd::jd-(3+mewd)];dt:_dj(jd);yy:$(yr:dt%10000);dd:$(d:dt!100);mm:$(mo:((dt-yr*10000)%100));arr::arr,$(yy,"-",(2$mm),"-",(2$dd))} lfd1: {[y];arr::(); m:1; do[12;lfd[m;y];m+:1]} main: {[y]; lfd1[y];`0: ,"Dates of last Fridays of ",($y);12 10#arr}

</lang> The output of a session is given below:

Output:

K Console - Enter \ for help

  \l lastfridt
  main 2012
Dates of last Fridays of 2012
("2012- 1-27"
 "2012- 2-24"
 "2012- 3-30"
 "2012- 4-27"
 "2012- 5-25"
 "2012- 6-29"
 "2012- 7-27"
 "2012- 8-31"
 "2012- 9-28"
 "2012-10-26"
 "2012-11-30"
 "2012-12-28")

Kotlin

<lang scala>// version 1.0.6

import java.util.*

fun main(args: Array<String>) {

   print("Enter a year : ")
   val year = readLine()!!.toInt()
   
   println("The last Fridays of each month in $year are as follows:")
   val calendar = GregorianCalendar(year, 0, 31)
   for (month in 1..12) {
       val daysInMonth = calendar.getActualMaximum(Calendar.DAY_OF_MONTH)
       var offset = calendar[Calendar.DAY_OF_WEEK] - Calendar.FRIDAY
       if (offset < 0) offset += 7
       val lastFriday = daysInMonth - offset
       println("$year-" + "%02d-".format(month) + "%02d".format(lastFriday))
       if (month < 12) {
           calendar.add(Calendar.DAY_OF_MONTH, 1)
           calendar.add(Calendar.MONTH, 1)
           calendar.add(Calendar.DAY_OF_MONTH, -1)
       }
   }

}</lang>

Output:

Enter a year : 2012
The last Fridays of each month in 2012 are as follows:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Lasso

<lang Lasso>define isLeapYear(y::integer) => { #y % 400 == 0 ? return true #y % 100 == 0 ? return false #y % 4 == 0 ? return true return false } define fridays(y::integer) => { local(out = array) loop(12) => { local(last = 28) loop_count == 2 && isLeapYear(#y) ? #last = 29 array(4,6,9,11) >> loop_count ? #last == 30 #last == 28 && loop_count != 2 ? #last = 31 local(start = date(-year=#y,-month=loop_count,-day=#last)) while(#start->dayofweek != 6) => { #start->subtract(-day=1) } #out->insert(#start) } return #out } with f in fridays(2012) do => {^ #f->format('%Q') + '\r' ^}</lang>

Output:

LiveCode

<lang LiveCode>function lastFriday yyyy

   -- year,month num,day of month,hour in 24-hour time,minute,second,numeric day of week.
   convert the long date to dateitems
   put 1 into item 2 of it
   put 1 into item 3 of it
   put yyyy into item 1 of it
   put it into startDate
   convert startDate to dateItems
   repeat with m = 1 to 12
       put m into item 2 of startDate
       repeat with d = 20 to 31
           put d into item 3 of startDate
           convert startDate to dateItems
           -- 6 is friday
           if item 7 of startDate is 6 and item 1 of startDate is yyyy and item 2 of startDate is m then
               put item 3 of startDate into fridays[item 2 of startDate]
           end if
       end repeat
   end repeat
   combine fridays using cr and space
   sort fridays ascending numeric
   return fridays

end lastFriday</lang> Example<lang LiveCode>put lastFriday("2012")</lang>Output<lang LiveCode>1 27 2 24 3 30 4 27 5 25 6 29 7 27 8 31 9 28 10 26 11 30 12 28</lang>

Logo

<lang logo>; Determine if a Gregorian calendar year is leap to leap? :year

 output (and 
   equal? 0 modulo :year 4
   not member? modulo :year 400 [100 200 300]
 )

end

Convert Gregorian calendar date to a simple day count from
RD 1 = January 1, 1 CE

to day_number :year :month :day

 local "elapsed make "elapsed difference :year 1
 output (sum  product 365 :elapsed
             int quotient :elapsed 4
             minus int quotient :elapsed 100
             int quotient :elapsed 400
             int quotient difference product 367 :month 362 12
             ifelse lessequal? :month 2 0 ifelse leap? :year -1 -2
             :day)

end

Find the day of the week from a day number, 0 = Sunday through 6 = Saturday

to day_of_week :day_number

 output modulo :day_number 7

end

Find the date of the last Friday of a given month

to last_friday :year :month

 local "zero make "zero day_number :year :month 0
 local "last make "last day_number :year sum 1 :month 0
 local "wday make "wday day_of_week :last
 local "friday make "friday sum :last remainder difference -2 :wday 7
 output difference :friday :zero

end

local "year make "year ifelse empty? :command.line 2012 :command.line

repeat 12 [

 local "month make "month #
 local "day make "day last_friday :year :month
 if (less? :month 10) [make "month word "0 :month]
 print reduce [(word ?1 "- ?2)] (list :year :month :day)

] bye</lang>

Output:

$  logo last_fridays.lg - 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Lua

<lang lua>function isLeapYear (y)

   return (y % 4 == 0 and y % 100 ~=0) or y % 400 == 0

end

function dayOfWeek (y, m, d)

   local t = os.time({year = y, month = m, day = d})
   return os.date("%A", t)

end

function lastWeekdays (wday, year)

   local monthLength, day = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
   if isLeapYear(year) then monthLength[2] = 29 end
   for month = 1, 12 do
       day = monthLength[month]
       while dayOfWeek(year, month, day) ~= wday do day = day - 1 end
       print(year .. "-" .. month .. "-" .. day)
   end

end

lastWeekdays("Friday", tonumber(arg[1]))</lang> Command line session:

>lua lastFridays.lua 2012
2012-1-27
2012-2-24
2012-3-30
2012-4-27
2012-5-25
2012-6-29
2012-7-27
2012-8-31
2012-9-28
2012-10-26
2012-11-30
2012-12-28

>

Maple

<lang Maple>fridays := proc(year) local i, dt, change, last_days; last_days := [31,28,31,30,31,30,31,31,30,31,30,31]; if (Calendar:-IsLeapYear(year)) then last_days[2] := 28; end if; for i to 12 do dt := Date(year, i, last_days[i]); change := 0; if not(Calendar:-DayOfWeek(dt) = 6) then change := -(Calendar:-DayOfWeek(dt) mod 7)-1; end if; dt := Calendar:-AdjustDateField(dt, "date", change); printf("%d-%d-%d\n", year, Month(dt), DayOfMonth(dt)); end do; end proc;

fridays(2012);</lang>

Output:

Mathematica/Wolfram Language

<lang Mathematica>FridaysOfYear[Y_] :=

NestWhile[(DaysPlus[#, - 1]) &, #, (DateString[#, "DayName"] != "Friday") &] & /@ 
 Most@Reverse@NestList [DaysPlus[# /. {x_, y_, X_} -> {x, y, 1}, - 1] &, {Y + 1, 1, 1}, 12]

Column@FridaysOfYear[2012]</lang>

Output:

{2012,1,27}
{2012,2,24}
{2012,3,30}
{2012,4,27}
{2012,5,25}
{2012,6,29}
{2012,7,27}
{2012,8,31}
{2012,9,28}
{2012,10,26}
{2012,11,30}
{2012,12,28}

MATLAB / Octave

<lang Matlab> function t = last_fridays_of_year(y)

 t1 = datenum([y,1,1,0,0,0]);
 t2 = datenum([y,12,31,0,0,0]);
 t  = datevec(t1:t2);
 t  = t(strmatch('Friday', datestr(t,'dddd')), :);     % find all Fridays
 t  = t([find(diff(t(:,2)) > 0); end], :);     % find Fridays before change of month
 end;

 datestr(last_fridays_of_year(2012),'yyyy-mm-dd')

</lang>

Output:

Maxima

<lang maxima>weekday(year, month, day) := block([m: month, y: year, k],

  if m < 3 then (m: m + 12,  y: y - 1), 
  k: 1 + remainder(day + quotient((m + 1)*26,  10) + y + quotient(y,  4)
       + 6*quotient(y,  100) + quotient(y,  400) + 5,  7), 
  ['monday,  'tuesday,  'wednesday,  'thurdsday,  'friday,  'saturday,  'sunday][k]

)$

leapyearp(year) := is(mod(year, 4) = 0 and (mod(year, 100) # 0 or mod(year, 400) = 0))$

lastfridays(year) := block(

  [m: [31,  if leapyearp(year) then 29 else 28,  31,  30,  31,  30,  31,  31,  30,  31,  30,  31],  v: [ ]], 
  for month thru 12 do v: endcons(sconcat(year,  "-",  month,  "-", 
     lmax(sublist(makelist(i,  i,  1,  m[month]),  lambda([day],  weekday(year,  month,  day) = 'friday)))),  v), 
  v

)$

lastfridays(2012); ["2012-1-27", "2012-2-24", "2012-3-30", "2012-4-27", "2012-5-25", "2012-6-29", "2012-7-27","2012-8-31", "2012-9-28", "2012-10-26", "2012-11-30", "2012-12-28"]</lang>

Nanoquery

<lang Nanoquery>import Nanoquery.Util

// a function to check if a year is a leap year def isLeapYear(year) if (year % 100 = 0) return (year % 400 = 0) else return (year % 4 = 0) end end

// a function to format 1-digit numbers as "0x" def form(num) if (num > 9) return str(num) else return "0" + str(num) end end

// get a year from the console print "enter year: " year = int(input())

// build a list of the expected amount of days for each month days = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31} if isLeapYear($year) days[1] = 29 end

// loop through each month for month in range(1, len($days)) // loop through each day of the month friday = null for day in range(1, days[month - 1]) // create a date object for this date date = new(Date) date.setYear(year).setMonth(month).setDay(day)

// check if it's a friday if (date.getDayOfWeek() = "Friday") // if it is, keep it friday = new(Date, date) end end for

// display the last friday found print friday.getYear() + "-" print form(friday.getMonth()) + "-" println form(friday.getDay()) end</lang>

NetRexx

Translation of: Java

Translation of: C

Implements the algorithms from both the Java and C implementations. <lang NetRexx>/* NetRexx */ options replace format comments java crossref symbols nobinary

import java.text.

runSample(arg) return

-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method lastFridayByLib(year) public static

 cal = GregorianCalendar(year, 0, 1)

 loop mon over DateFormatSymbols().getShortMonths()
   if \mon.isEmpty() then do
     totalDaysOfMonth = cal.getActualMaximum(Calendar.DAY_OF_MONTH)
     cal.set(Calendar.DAY_OF_MONTH, totalDaysOfMonth)

     daysToRollBack = (cal.get(Calendar.DAY_OF_WEEK) + 1) // 7

     day = totalDaysOfMonth - daysToRollBack
     cal.set(Calendar.DAY_OF_MONTH, day)

     say year.right(4, 0) mon day.right(2, 0)

     cal.set(year, cal.get(Calendar.MONTH) + 1, 1)
     end
   end mon
 return

-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method lastFridayCalc(year) public static binary signals BadArgumentException

 if year <= 1700 then do
   signal BadArgumentException(year 'is out of range')
   end

 wk  = int
 mth = int
 yr  = int year
 days = [int 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]  -- days in month
 days[1] = days[1] - ((yr // 4) | \(yr // 100) & (yr // 400)) -- adjust for leap year

 wk = yr * 365 + (yr - 1) % 4 - (yr - 1) % 100 + (yr - 1) % 400 + 6 -- week number

 loop mth = 0 to 11
   wk = (wk + days[mth]) // 7
   wx = int
   if wk < 5 then wx = -2
             else wx = 5
   yy = Rexx(yr)
   mm = Rexx(mth + 1)
   dd = Rexx(days[mth] + wx - wk)
   say yy.right(4, 0)'-'mm.right(2, 0)'-'dd.right(2, 0)
   end mth
 return

-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method runSample(arg) private static

 do
   parse arg year .
   if year =  | year = '.' then year = 2012
   dlm = '-'
   dlm = dlm.left(60, dlm)
   say
   say 'Using Java calendar libraries'
   say dlm
   lastFridayByLib(year)
   say
   say 'Calculated'
   say dlm
   lastFridayCalc(year)
 catch ex = Exception
   ex.printStackTrace
 end
 return

</lang>

Output:

Using Java calendar libraries
------------------------------------------------------------
2012 Jan 27
2012 Feb 24
2012 Mar 30
2012 Apr 27
2012 May 25
2012 Jun 29
2012 Jul 27
2012 Aug 31
2012 Sep 28
2012 Oct 26
2012 Nov 30
2012 Dec 28

Calculated
------------------------------------------------------------
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Nim

<lang nim>import os, strutils, times

const

 DaysInMonth: array[Month, int] = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
 DayDiffs:  array[WeekDay, int] = [3, 4, 5, 6, 0, 1, 2]

let year = paramStr(1).parseInt

for month in mJan..mDec:

 var lastDay = DaysInMonth[month]
 if month == mFeb and year.isLeapYear: lastDay = 29
 var date = initDateTime(lastDay, month, year, 0, 0, 0)
 date = date - days(DayDiffs[date.weekday])
 echo date.format("yyyy-MM-dd")</lang>

Output:

Sample usage: ./lastfridays 2012

OCaml

Using the module Unix from the standard OCaml library:

<lang ocaml>#load "unix.cma" open Unix

let usage() =

 Printf.eprintf "%s <year>\n" Sys.argv.(0);
 exit 1

let print_date t =

 Printf.printf "%d-%02d-%02d\n" (t.tm_year + 1900) (t.tm_mon + 1) t.tm_mday

let is_date_ok tm t =

 (tm.tm_year = t.tm_year &&
  tm.tm_mon  = t.tm_mon  &&
  tm.tm_mday = t.tm_mday)

let () =

 let _year =
   try int_of_string Sys.argv.(1)
   with _ -> usage()
 in
 let year = _year - 1900 in
 let fridays = Array.make 12 (Unix.gmtime 0.0) in
 for month = 0 to 11 do
   for day_of_month = 1 to 31 do
     let tm = { (Unix.gmtime 0.0) with 
       tm_year = year;
       tm_mon = month;
       tm_mday = day_of_month;
     } in
     let _, t = Unix.mktime tm in
     if is_date_ok tm t  (* check for months that have less than 31 days *)
     && t.tm_wday = 5  (* is a friday *)
     then fridays.(month) <- t
   done;
 done;
 Array.iter print_date fridays</lang>

Output:

$ ocaml last_fridays.ml 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

With a dedicated library

Library: OCaml Calendar Library

<lang ocaml>open CalendarLib

let usage() =

 Printf.eprintf "%s <year>\n" Sys.argv.(0);
 exit 1

let print_date (year, month, day) =

 Printf.printf "%d-%02d-%02d\n" year month day

let () =

 let year =
   try int_of_string Sys.argv.(1)
   with _ -> usage()
 in
 let fridays = ref [] in
 for month = 1 to 12 do
   let num_days = Date.days_in_month (Date.make_year_month year month) in
   let rec aux day =
     if Date.day_of_week (Date.make year month day) = Date.Fri
     then fridays := (year, month, day) :: !fridays
     else aux (pred day)
   in
   aux num_days
 done;
 List.iter print_date (List.rev !fridays)</lang>

Run this script with the command:

ocaml unix.cma str.cma -I +calendar calendarLib.cma last_fridays.ml 2012

Oforth

<lang Oforth>import: date

lastFridays(y)

| m |

  Date.JANUARY Date.DECEMBER for: m [
     Date newDate(y, m, Date.DaysInMonth(y, m))
     while(dup dayOfWeek Date.FRIDAY <>) [ addDays(-1) ]
     println
     ] ;</lang>

Output:

2012-01-27 00:00:00,000
2012-02-24 00:00:00,000
2012-03-30 00:00:00,000
2012-04-27 00:00:00,000
2012-05-25 00:00:00,000
2012-06-29 00:00:00,000
2012-07-27 00:00:00,000
2012-08-31 00:00:00,000
2012-09-28 00:00:00,000
2012-10-26 00:00:00,000
2012-11-30 00:00:00,000
2012-12-28 00:00:00,000

PARI/GP

<lang parigp>\\ Normalized Julian Day Number from date njd(D) = {

 my (m = D[2], y = D[1]);

 if (D[2] > 2, m++, y--; m += 13);

 (1461 * y) \ 4 + (306001 * m) \ 10000 + D[3] - 694024 + 2 - y \ 100 + y \ 400

}

\\ Date from Normalized Julian Day Number njdate(J) = {

 my (a = J + 2415019, b = (4 * a - 7468865) \ 146097, c, d, m, y);

 a += 1 + b - b \ 4 + 1524;
 b = (20 * a - 2442) \ 7305;
 c = (1461 * b) \ 4;
 d = ((a - c) * 10000) \ 306001;
 m = d - 1 - 12 * (d > 13);
 y = b - 4715 - (m > 2);
 d = a - c - (306001 * d) \ 10000;

 [y, m, d]

}

for (m=1, 12, a=njd([2012,m+1,0]); print(njdate(a-(a+1)%7)))</lang>

Output:

[2012, 1, 27]
[2012, 2, 24]
[2012, 3, 30]
[2012, 4, 27]
[2012, 5, 25]
[2012, 6, 29]
[2012, 7, 27]
[2012, 8, 31]
[2012, 9, 28]
[2012, 10, 26]
[2012, 11, 30]
[2012, 12, 28]

Perl

<lang Perl>#!/usr/bin/perl -w use strict ; use DateTime ; use feature qw( say ) ;

foreach my $month ( 1..12 ) {

  my $dt = DateTime->last_day_of_month( year => $ARGV[ 0 ] , month => $month ) ;
  while ( $dt->day_of_week != 5 ) {
     $dt->subtract( days => 1 ) ;
  }
  say $dt->ymd ;

}</lang>

Output:

Phix

Requires 0.8.1+ (day_of_week() is now ISO 8601 compliant, plus this now uses a new routine: day_of_week()). <lang Phix>procedure last_day_of_month(integer y, dow)

   for m=1 to 12 do
       integer d = days_in_month(y,m),
               a = dow-day_of_week(y,m,d)
       printf(1,"%4d-%02d-%02d\n",{y,m,d+a-7*(a>0)})
   end for

end procedure constant FRIDAY=5 last_day_of_month(prompt_number("Year:",{1752,9999}),FRIDAY)</lang>

Output:

Year:2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

PHP

PHP is generally used for web apps, so I am not implementing the command-line component of this task.

<lang PHP><?php function last_friday_of_month($year, $month) {

 $day = 0;
 while(True) {
   $last_day = mktime(0, 0, 0, $month+1, $day, $year); 
   if (date("w", $last_day) == 5) {
     return date("Y-m-d", $last_day);
   }
   $day -= 1;
 }

}

function print_last_fridays_of_month($year) {

 foreach(range(1, 12) as $month) {
   echo last_friday_of_month($year, $month), "
";
 }

}

date_default_timezone_set("GMT"); $year = 2012; print_last_fridays_of_month($year); ?></lang>

Output:

PicoLisp

<lang PicoLisp>(de lastFridays (Y)

  (for M 12
     (prinl
        (dat$
           (find '((D) (= "Friday" (day D)))
              (mapcar '((D) (date Y M D)) `(range 31 22)) )
           "-" ) ) ) )</lang>

Test: <lang PicoLisp>: (lastFridays 2012) 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28</lang>

Pike

<lang Pike>int(0..1) last_friday(object day) {

  return day->week_day() == 5 && 
         day->month_day() > day->month()->number_of_days()-7;

}

int main(int argc, array argv) {

   array days = filter(Calendar.Year((int)argv[1])->months()->days()[*], last_friday);
   write("%{%s\n%}", days->format_ymd());
   return 0;

}</lang>

PL/I

<lang PL/I> Fridays: procedure (year) options (main); /* 8 January 2013 */

  declare year character (4) varying;
  declare start fixed binary (31);
  declare months fixed decimal (2) initial (0);
  declare (current_month, month_one_week_hence) character (2);

  put list ('Last Fridays in each month for the year ' || year || ':' );
  start = days('0101' || year, 'DDMMYYYY');
  /* Find first Friday */
  do while (weekday(start) ^= 6); start = start + 1; end;

  do until (months=12);
     current_month = substr (daystodate(start, 'MMDDYYYY'), 1, 2 );
     month_one_week_hence = substr (daystodate(start+7, 'MMDDYYYY'), 1, 2 );
     if current_month ^= month_one_week_hence then
        do;
           months = months + 1;
           put skip list (daystodate(start, 'DDMmmYYYY'));
        end;
     start = start + 7;
  end;

end Fridays; </lang> The command: FRIDAYS /2008 produces:

Last Fridays in each month for the year 2008:
25Jan2008 
29Feb2008 
28Mar2008 
25Apr2008 
30May2008 
27Jun2008 
25Jul2008 
29Aug2008 
26Sep2008 
31Oct2008 
28Nov2008 
26Dec2008

Output:

for 2013

Last Fridays in each month for the year 2013: 
25Jan2013 
22Feb2013 
29Mar2013 
26Apr2013 
31May2013 
28Jun2013 
26Jul2013 
30Aug2013 
27Sep2013 
25Oct2013 
29Nov2013 
27Dec2013

PowerShell

<lang PowerShell> function last-dayofweek {

   param(
    [Int][ValidatePattern("[1-9][0-9][0-9][0-9]")]$year,
    [String][validateset('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday')]$dayofweek
   )
   $date = (Get-Date -Year $year -Month 1 -Day 1)
   while($date.DayOfWeek -ne $dayofweek) {$date = $date.AddDays(1)}
   while($date.year -eq $year) {
       if($date.Month -ne $date.AddDays(7).Month) {$date.ToString("yyyy-dd-MM")}
       $date = $date.AddDays(7)
   }

} last-dayofweek 2012 "Friday" </lang> Output:

Alternate Version

This script finds the first and/or last or all dates of any of the days of week; accepts [Int32] and [DateTime] values for Month and Year parameters; outputs [DateTime] objects by default but has an option to output time strings in various formats. This script also allows for pipeline input based mainly upon the Month parameter. This script has a syntax as complex as any PowerShell Cmdlet because it attempts to do everything. <lang PowerShell> function Get-Date0fDayOfWeek {

   [CmdletBinding(DefaultParameterSetName="None")]
   [OutputType([datetime])]
   Param
   (
       [Parameter(Mandatory=$false,
                  ValueFromPipeline=$true,
                  ValueFromPipelineByPropertyName=$true,
                  Position=0)]
       [ValidateRange(1,12)]
       [int]
       $Month = (Get-Date).Month,

       [Parameter(Mandatory=$false,
                  ValueFromPipelineByPropertyName=$true,
                  Position=1)]
       [ValidateRange(1,9999)]
       [int]
       $Year = (Get-Date).Year,

       [Parameter(Mandatory=$true, ParameterSetName="Sunday")]
       [switch]
       $Sunday,

       [Parameter(Mandatory=$true, ParameterSetName="Monday")]
       [switch]
       $Monday,

       [Parameter(Mandatory=$true, ParameterSetName="Tuesday")]
       [switch]
       $Tuesday,

       [Parameter(Mandatory=$true, ParameterSetName="Wednesday")]
       [switch]
       $Wednesday,

       [Parameter(Mandatory=$true, ParameterSetName="Thursday")]
       [switch]
       $Thursday,

       [Parameter(Mandatory=$true, ParameterSetName="Friday")]
       [switch]
       $Friday,

       [Parameter(Mandatory=$true, ParameterSetName="Saturday")]
       [switch]
       $Saturday,

       [switch]
       $First,

       [switch]
       $Last,

       [switch]
       $AsString,

       [Parameter(Mandatory=$false)]
       [ValidateNotNullOrEmpty()]
       [string]
       $Format = "dd-MMM-yyyy"
   )

   Process
   {
       [datetime[]]$dates = 1..[DateTime]::DaysInMonth($Year,$Month) | ForEach-Object {
           Get-Date -Year $Year -Month $Month -Day $_ -Hour 0 -Minute 0 -Second 0 |
           Where-Object -Property DayOfWeek -Match $PSCmdlet.ParameterSetName
       }

       if ($First -or $Last)
       {
           if ($AsString)
           {
               if ($First) {$dates[0].ToString($Format)}
               if ($Last)  {$dates[-1].ToString($Format)}
           }
           else
           {
               if ($First) {$dates[0]}
               if ($Last)  {$dates[-1]}
           }
       }
       else
       {
           if ($AsString)
           {
               $dates | ForEach-Object {$_.ToString($Format)}
           }
           else
           {
               $dates
           }
       }
   }

} </lang> The default is to return [DateTime] objects: <lang PowerShell> 1..12 | Get-Date0fDayOfWeek -Year 2012 -Last -Friday </lang>

Output:

Friday, January 27, 2012 12:00:00 AM
Friday, February 24, 2012 12:00:00 AM
Friday, March 30, 2012 12:00:00 AM
Friday, April 27, 2012 12:00:00 AM
Friday, May 25, 2012 12:00:00 AM
Friday, June 29, 2012 12:00:00 AM
Friday, July 27, 2012 12:00:00 AM
Friday, August 31, 2012 12:00:00 AM
Friday, September 28, 2012 12:00:00 AM
Friday, October 26, 2012 12:00:00 AM
Friday, November 30, 2012 12:00:00 AM
Friday, December 28, 2012 12:00:00 AM

Return the [DateTime] objects as strings (using the default string format): <lang PowerShell> 1..12 | Get-Date0fDayOfWeek -Year 2012 -Last -Friday -AsString </lang>

Output:

27-Jan-2012
24-Feb-2012
30-Mar-2012
27-Apr-2012
25-May-2012
29-Jun-2012
27-Jul-2012
31-Aug-2012
28-Sep-2012
26-Oct-2012
30-Nov-2012
28-Dec-2012

Return the [DateTime] objects as strings (specifying the string format): <lang PowerShell> 1..12 | Get-Date0fDayOfWeek -Year 2012 -Last -Friday -AsString -Format yyyy-MM-dd </lang>

Output:

PureBasic

<lang PureBasic>Procedure LastFridayOfEachMonth(yyyy.i,List lfem.i())

 Define dv.i=ParseDate("%yyyy",Str(yyyy)), mv.i=1
 NewList d.i()
 For d=1 To 365 
   dv=AddDate(dv,#PB_Date_Day,1)
   If DayOfWeek(dv)=5
     AddElement(d()) : d()=dv
   EndIf    
 Next 
 dv=0
 For mv=1 To 12
   ForEach d()
     If dv<d() And Month(d())=mv
       dv=d()
     EndIf
   Next
   AddElement(lfem()) : lfem()=dv
 Next

EndProcedure

NewList lf.i() Define y.i OpenConsole("Last Friday of each month") Print("Input Year [ 1971 < y < 2038 ]: ") y=Val(Input()) If y>1971 And y<2038

 PrintN("Last Friday of each month...")
 LastFridayOfEachMonth(y,lf())
 ForEach lf()
   PrintN(FormatDate("%dd.%mm.%yyyy",lf()))
 Next

EndIf Print("...End") Input()</lang>

Output:

Input Year [ 1971 < y < 2038 ]: 2017
Last Friday of each month...
27.01.2017
24.02.2017
31.03.2017
28.04.2017
26.05.2017
30.06.2017
28.07.2017
25.08.2017
29.09.2017
27.10.2017
24.11.2017
29.12.2017
...End

Python

<lang python>import calendar

def last_fridays(year):

   for month in range(1, 13):
       last_friday = max(week[calendar.FRIDAY]
           for week in calendar.monthcalendar(year, month))
       print('{:4d}-{:02d}-{:02d}'.format(year, month, last_friday))</lang>

Output:

>>> last_fridays(2012)
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Another solution <lang python>import calendar c=calendar.Calendar() fridays={} year=raw_input("year") for item in c.yeardatescalendar(int(year)):

   for i1 in item:
       for i2 in i1:
           for i3 in i2:
               if "Fri" in i3.ctime() and year in i3.ctime():
                   month,day=str(i3).rsplit("-",1)
                   fridays[month]=day

for item in sorted((month+"-"+day for month,day in fridays.items()),

                  key=lambda x:int(x.split("-")[1])):
   print item</lang>

Using reduce

<lang python>import calendar c=calendar.Calendar() fridays={} year=raw_input("year") add=list.__add__ for day in reduce(add,reduce(add,reduce(add,c.yeardatescalendar(int(year))))):

   if "Fri" in day.ctime() and year in day.ctime():
       month,day=str(day).rsplit("-",1)
       fridays[month]=day

for item in sorted((month+"-"+day for month,day in fridays.items()),

                  key=lambda x:int(x.split("-")[1])):
   print item</lang>

using itertools

<lang python>import calendar from itertools import chain f=chain.from_iterable c=calendar.Calendar() fridays={} year=raw_input("year") add=list.__add__

for day in f(f(f(c.yeardatescalendar(int(year))))):

   if "Fri" in day.ctime() and year in day.ctime():
       month,day=str(day).rsplit("-",1)
       fridays[month]=day

for item in sorted((month+"-"+day for month,day in fridays.items()),

                  key=lambda x:int(x.split("-")[1])):
   print item</lang>

Quackery

<lang Quackery> [ over 3 < if [ 1 - ]

   dup 4 / over +
   over 100 / -
   swap 400 / +
   swap 1 - 
   [ table 
     0 3 2 5 0 3
     5 1 4 6 2 4 ]
   + + 7 mod ]                     is dayofweek  ( day month year --> weekday )

 [ dup 400 mod 0 = iff
     [ drop true ]  done
   dup 100 mod 0 = iff
     [ drop false ] done
   4 mod 0 = ]                     is leap       (           year --> b       )

 [ swap 1 -
   [ table
     31 [ dup leap 28 + ]
     31 30 31 30 31 31 30
     31 30 31 ]
   do nip ]                        is monthdays  (     month year --> n       )

 [ number$
   2 times
     [ char - join
       over 10 < if 
         [ char 0 join ]
       swap number$ join ] 
     echo$ ]                       is echoymd    ( day month year -->         )

 [ dip
     [ 2dup monthdays
       dup temp put
       unrot dayofweek ]
   - dup 0 < if [ 7 + ]
   temp take swap - ]              is lastwkday  ( month year wkd --> n       )

 [ temp put 
   12 times
     [ i^ 1+ over
       2dup temp share lastwkday 
       unrot echoymd cr ] 
   drop temp release ]            is lastwkdays  (       year wkd -->        )

 [ 5 lastwkdays ]                 is lastfridays (           year -->        )

 2012 lastfridays</lang>

Output:

R

<lang rsplus>year = commandArgs(T) d = as.Date(paste0(year, "-01-01")) fridays = d + seq(by = 7,

   (5 - as.POSIXlt(d)$wday) %% 7,
   364 + (months(d + 30 + 29) == "February"))

message(paste(collapse = "\n", fridays[tapply(

   seq_along(fridays), as.POSIXlt(fridays)$mon, max)]))</lang>

Racket

lang racket

(require srfi/19 math)

(define (days-in-month m y)

 (define lengths #(0 31 #f 31 30 31 30 31 31 30 31 30 31))
 (define d (vector-ref lengths m))
 (or d (days-in-feb y)))

(define (leap-year? y)

 (and (divides? 4 y)
      (or (not (divides? 100 y))
          (divides? 400 y))))

(define (days-in-feb y)

 (if (leap-year? y) 29 28))

(define (last-day-in-month m y)

 (make-date 0 0 0 0 (days-in-month m y) m y 0))

(define (week-day date)

 (define days #(sun mon tue wed thu fri sat))
 (vector-ref days (date-week-day date)))

(define (last-fridays y)

 (for/list ([m (in-range 1 13)])
   (prev-friday (last-day-in-month m y))))

(define 24hours (make-time time-duration 0 (* 24 60 60)))

(define (prev-day d)

 (time-utc->date
  (subtract-duration 
   (date->time-utc d) 24hours)))

(define (prev-friday d)

 (if (eq? (week-day d) 'fri)
     d
     (prev-friday (prev-day d))))

(for ([d (last-fridays 2012)])

 (displayln (~a (date->string d "~a ~d ~b ~Y"))))

</lang>

Output:

Fri 27 Jan 2012
Fri 24 Feb 2012
Fri 30 Mar 2012
Fri 27 Apr 2012
Fri 25 May 2012
Fri 29 Jun 2012
Fri 27 Jul 2012
Fri 31 Aug 2012
Fri 28 Sep 2012
Fri 26 Oct 2012
Fri 30 Nov 2012
Fri 28 Dec 2012

Raku

(formerly Perl 6) <lang perl6>sub MAIN (Int $year = Date.today.year) {

   my @fri;
   for Date.new("$year-01-01") .. Date.new("$year-12-31") {
       @fri[.month] = .Str if .day-of-week == 5;
   }
   .say for @fri[1..12];

}</lang>

Example:

$ ./lastfri 2038
2038-01-29
2038-02-26
2038-03-26
2038-04-30
2038-05-28
2038-06-25
2038-07-30
2038-08-27
2038-09-24
2038-10-29
2038-11-26
2038-12-31

A solution without a result array to store things in:

<lang perl6>sub MAIN (Int $year = Date.today.year) {

   say ~.value.reverse.first: *.day-of-week == 5
       for classify *.month, Date.new("$year-01-01") .. Date.new("$year-12-31");

}</lang>

Here, classify sorts the dates into one bin per month (but preserves the order in each bin). We then take the list inside each bin (.value) and find the last (.reverse.first) date which is a Friday.

Another variation where the data flow can be read left to right using feed operators:

<lang perl6>sub MAIN (Int $year = Date.today.year) {

   .say for Date.new("$year-01-01") .. Date.new("$year-12-31") ==> classify *.month ==>
            map *.value.reverse.first: *.day-of-week == 5

}</lang>

REBOL

The longer version: <lang REBOL>leap-year?: function [year] [to-logic attempt [to-date reduce [29 2 year]]]

days-in-feb: function [year] [either leap-year? year [29] [28]]

days-in-month: function [month year] [

   do pick [31 (days-in-feb year) 31 30 31 30 31 31 30 31 30 31] month

]

last-day-of-month: function [month year] [

   to-date reduce [year month  days-in-month month year]

]

last-weekday-of-month: function [weekday month year] [

   d: last-day-of-month month year
   while [d/weekday != weekday] [d/day: d/day - 1]
   d

]

last-friday-of-month: function [month year] [last-weekday-of-month 5 month year]

year: to-integer input repeat month 12 [print last-friday-of-month month year] </lang>

Output:

rebol last-fridays.reb <<< 2012
27-Jan-2012
24-Feb-2012
30-Mar-2012
27-Apr-2012
25-May-2012
29-Jun-2012
27-Jul-2012
31-Aug-2012
28-Sep-2012
26-Oct-2012
30-Nov-2012
28-Dec-2012

A shorter version: <lang REBOL>last-fridays-of-year: function [year] [

   collect [
       repeat month 12 [
           d: to-date reduce [1 month year]
           d/month: d/month + 1                      ; start of next month
           until [d/day: d/day - 1  d/weekday = 5]   ; go backwards until find a Friday  
           keep d
       ]
   ]

]

foreach friday last-fridays-of-year to-integer input [print friday] </lang> NB. See "Find the last Sunday of each month" Rosetta for alternative (even more succinct) solution

REXX

This REXX program will find the last day-of-week (for any day) of all the months for any year.
It wasn't optimized just to find a particular day-of-week.

The documentation for the lastDOW function (used in the REXX program below):

 ╔════════════════════════════════════════════════════════════════════════════════════════════════╗
 ║ lastDOW:  procedure to return the date of the  last day─of─week of any particular month of any ║
 ║           particular year.                                                                     ║
 ║                                                                                                ║
 ║ The  day─of─week  must be specified  (it can be in any case, (lower─/mixed─/upper─case)  as an ║ 
 ║ English name of the spelled day of the week,  with a minimum length that causes no ambiguity.  ║
 ║                                                                                                ║
 ║ I.E.:    TU  for Tuesday.    W  for Wednesday,     Sa  for Saturday,     Su  for Sunday ...    ║
 ║                                                                                                ║
 ║ The month can be specified as an integer  1 ──► 12                                             ║                               
 ║    1=January     2=February     3=March     4=April     5=May     6=June    ...   12=December  ║
 ║ or the English  name  of the month,  with a minimum length that causes no ambiguity.           ║
 ║ I.E.:    JA  for January,   AP  for April,   JUN  for June,   JUL  for July,   D  for December.║
 ║ If omitted  [or an asterisk(*)],  the current month is used.                                   ║
 ║                                                                                                ║
 ║ The year is specified as an integer or just the last two digits  (two digit years are assumed  ║
 ║ to be in the current century,  and there is no windowing for a two─digit year).  If omitted    ║
 ║ [or an asterisk(*)],  the current year is used.     Years < 100   must be specified with  (at  ║
 ║ least 2)  leading zeroes.                                                                      ║
 ║                                                                                                ║
 ║ The method used is:  find the "day number" of the 1st of the next month and then subtract one  ║
 ║ (this gives the "day number" of the last day of the month,  bypassing the leapday mess).  The  ║
 ║ last day─of─week is then obtained straightforwardly,   or  via subtraction.                    ║
 ╚════════════════════════════════════════════════════════════════════════════════════════════════╝

<lang rexx>/*REXX program displays the dates of the last Fridays of each month for any given year.*/ parse arg yyyy /*obtain optional argument from the CL.*/

                do j=1  for 12                  /*traipse through all the year's months*/
                say lastDOW('Friday', j, yyyy)  /*find last Friday for the  Jth  month.*/
                end  /*j*/

exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ lastDOW: procedure; arg dow .,mm .,yy .; parse arg a.1,a.2,a.3 /*DOW = day of week*/ if mm== | mm=='*' then mm= left( date('U'), 2) /*use default month*/ if yy== | yy=='*' then yy= left( date('S'), 4) /*use default year */ if length(yy)==2 then yy= left( date('S'), 2)yy /*append century. */

                                        /*Note mandatory leading blank in strings below*/

$=" Monday TUesday Wednesday THursday Friday SAturday SUnday" !=" JAnuary February MARch APril MAY JUNe JULy AUgust September October November December" upper $ ! /*uppercase strings*/ if dow== then call .er "wasn't specified", 1 /*no month given ? */ if arg()>3 then call .er 'arguments specified', 4 /*too many args ? */

 do j=1  for 3                                                      /*any plural args ?*/
 if words( arg(j) ) > 1   then call .er 'is illegal:',   j          /*check if plural. */
 end
                                                                    /*find DOW in list.*/

dw= pos(' 'dow, $) /*find day-of-week*/ if dw==0 then call .er 'is invalid:' , 1 /*no DOW was found?*/ if dw\==lastpos(' 'dow,$) then call .er 'is ambiguous:', 1 /*check min length.*/

if datatype(mm, 'M') then do /*is MM alphabetic?*/

                          m= pos(' 'mm, !)                          /*maybe its good...*/
                          if m==0                   then call .er 'is invalid:'  ,   1
                          if m\==lastpos(' 'mm,!)   then call .er 'is ambiguous:',   2
                          mm= wordpos( word( substr(!,m), 1), !)-1  /*now, use true Mon*/
                          end

if \datatype(mm, 'W') then call .er "isn't an integer:", 2 /*MM (mon) ¬integer*/ if \datatype(yy, 'W') then call .er "isn't an integer:", 3 /*YY (yr) ¬integer*/ if mm<1 | mm>12 then call .er "isn't in range 1──►12:", 2 /*MM out─of─range. */ if yy=0 then call .er "can't be 0 (zero):", 3 /*YY can't be zero.*/ if yy<0 then call .er "can't be negative:", 3 /* " " " neg. */ if yy>9999 then call .er "can't be > 9999:", 3 /* " " " huge.*/

tdow= wordpos( word( substr($, dw), 1), $) - 1 /*target DOW, 0──►6*/

                                                                    /*day# of last dom.*/

_= date('B', right(yy + (mm=12), 4)right(mm // 12 + 1, 2, 0)"01", 'S') - 1 ?= _ // 7 /*calc. DOW, 0──►6*/ if ?\==tdow then _= _ - ? - 7 + tdow + 7 * (?>tdow) /*not DOW? Adjust.*/ return date('weekday', _, "B") date(, _, 'B') /*return the answer*/ /*──────────────────────────────────────────────────────────────────────────────────────*/ .er: arg ,_; say; say '***error*** (in LASTDOW)'; say /*tell error, and */

    say word('day-of-week month year excess', arg(2))  arg(1)  a._  /*plug in a choice.*/
    say;      exit 13                                               /*··· then exit.   */</lang>

output when using the following input of: 2012 or 12 </tt

Friday 27 Jan 2012 Friday 24 Feb 2012 Friday 30 Mar 2012 Friday 27 Apr 2012 Friday 25 May 2012 Friday 29 Jun 2012 Friday 27 Jul 2012 Friday 31 Aug 2012 Friday 28 Sep 2012 Friday 26 Oct 2012 Friday 30 Nov 2012 Friday 28 Dec 2012Ring<lang ring> see "What year to calculate (yyyy) : " give year see "Last Friday in " + year + " are on :" + nl month = list(12) mo = [4,0,0,3,5,1,3,6,2,4,0,2] mon = [31,28,31,30,31,30,31,31,30,31,30,31] if year < 2100 leap = year - 1900 else leap = year - 1904 ok m = ((year-1900)%7) + floor(leap/4) % 7 for n = 1 to 12month[n] = (mo[n] + m) % 7next for n = 1 to 12for i = (mon[n] - 6) to mon[n] if year%4 = 0 and n<3 x = (month[n] + i) % 7 - 1 else x = (month[n] + i) % 7 ok if n < 10 strn = "0" + string(n) else strn = string(n) ok if x = 2 see year + "-" + strn + "-" + string(i) + nl ok nextnext </lang> Output:What year to calculate (yyyy) : 2012 Last Fridays in 2012 are on : 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28Ruby<lang ruby>require 'date' def last_friday(year, month)# Last day of month: Date.new interprets a negative number as a relative month/day from the end of year/month. d = Date.new(year, month, -1) d -= (d.wday - 5) % 7 # Subtract days after Friday.end year = Integer(ARGV.shift) (1..12).each {|month| puts last_friday(year, month)}</lang> Friday is d.wday == 5; the expression (d.wday - 5) % 7 counts days after Friday.Output:2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28Or get the last day of the month and go to the previous day until it's a Friday. <lang ruby>require 'date' def last_friday(year, month)d = Date.new(year, month, -1) d = d.prev_day until d.friday? dend </lang>Run BASIC<lang runbasic>input "Year:";yr dayOne$ = "01-01-";yr n1 = date$(dayOne$) for i = 1 to 12n1 = n1 + 26 m1$ = left$(date$(n1),2) while m1$ = left$(date$(n1),2) ' find end of month n1 = n1 + 1 wend n1 = n1 -1 while (n1 Mod 7) <> 3 ' find Friday n1 = n1 - 1 wend print date$(n1) ' print last Friday's datenext i</lang>Year:?2013 01/25/2013 02/22/2013 03/29/2013 04/26/2013 05/31/2013 06/28/2013 07/26/2013 08/30/2013 09/27/2013 10/25/2013 11/29/2013 12/27/2013Rust<lang rust>use std::env::args; use time::{Date, Duration}; fn main() {let year = args().nth(1).unwrap().parse::<i32>().unwrap(); (1..=12) .map(|month| Date::try_from_ymd(year + month / 12, ((month % 12) + 1) as u8, 1)) .filter_map(|date| date.ok()) .for_each(|date| { let days_back = Duration::days(((date.weekday().number_from_sunday() as i64) % 7) + 1); println!("{}", date - days_back); });}</lang>Output:2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28Scala<lang scala>import java.util.Calendar import java.text.SimpleDateFormat object Fridays {def lastFridayOfMonth(year:Int, month:Int)={ val cal=Calendar.getInstance cal.set(Calendar.YEAR, year) cal.set(Calendar.MONTH, month) cal.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY) cal.set(Calendar.DAY_OF_WEEK_IN_MONTH, -1) cal.getTime }def fridaysOfYear(year:Int)=for(month <- 0 to 11) yield lastFridayOfMonth(year, month)def main(args:Array[String]){ val year=args(0).toInt val formatter=new SimpleDateFormat("yyyy-MMM-dd") fridaysOfYear(year).foreach{date=> println(formatter.format(date)) } }}</lang>Output:2012-Jan-27 2012-Feb-24 2012-Mrz-30 2012-Apr-27 2012-Mai-25 2012-Jun-29 2012-Jul-27 2012-Aug-31 2012-Sep-28 2012-Okt-26 2012-Nov-30 2012-Dez-28Seed7Uses the libraries time.s7i and duration.s7i. Applicable to any day of the week, cf. [[2]]. <lang seed7>$ include "seed7_05.s7i";include "time.s7i"; include "duration.s7i";const proc: main is funclocal var integer: weekday is 1; # 1 for monday, 2 for tuesday, and so on up to 7 for sunday. var integer: year is 0; var integer: month is 1; var time: aDate is time.value; var time: selected is time.value; begin if length(argv(PROGRAM)) <> 2 then writeln("usage: lastWeekdayInMonth weekday year"); writeln(" weekday: 1 for monday, 2 for tuesday, and so on up to 7 for sunday."); else weekday := integer parse (argv(PROGRAM)[1]); year := integer parse (argv(PROGRAM)[2]); for month range 1 to 12 do aDate := date(year, month, 1); while aDate.month = month do if dayOfWeek(aDate) = weekday then selected := aDate; end if; aDate +:= 1 . DAYS; end while; writeln(strDate(selected)); end for; end if; end func;</lang>Output:

when called with s7 rosetta/lastWeekdayInMonth 5 2013

2013-01-25 2013-02-22 2013-03-29 2013-04-26 2013-05-31 2013-06-28 2013-07-26 2013-08-30 2013-09-27 2013-10-25 2013-11-29 2013-12-27SenseTalk<lang sensetalk> ask "What year?" put it into year put !"The last Fridays of each month in year are:" set lastDayOfMonth to year & "-01-31" -- start with January 31 of the year repeat 12 times set lastFriday to lastDayOfMonth repeat until weekdayName of lastFriday is "Friday" subtract a day from lastFriday -- work back to Friday end repeat put the monthName of lastFriday && ordinalWords of the day of lastFriday add a month to lastDayOfMonth -- advance to last day of next month end repeat </lang>Output:The last Fridays of each month in 2008 are: January twenty-fifth February twenty-ninth March twenty-eighth April twenty-fifth May thirtieth June twenty-seventh July twenty-fifth August twenty-ninth September twenty-sixth October thirty-first November twenty-eighth December twenty-sixthSidefTranslation of: Perl<lang ruby>require('DateTime') var (year=2016) = ARGV.map{.to_i}... for month (1..12) {var dt = %O<DateTime>.last_day_of_month(year => year, month => month) while (dt.day_of_week != 5) { dt.subtract(days => 1) } say dt.ymd}</lang>Output:$ sidef lastfriday.sf 2012 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28Smalltalk<lang Smalltalk> Pharo Smalltalk [ :yr | | firstDay firstFriday |firstDay := Date year: yr month: 1 day: 1. firstFriday := firstDay addDays: (6 - firstDay dayOfWeek). (0 to: 53) collect: [ :each | firstFriday addDays: (each * 7) ] thenSelect: [ :each | (((Date daysInMonth: each monthIndex forYear: yr) - each dayOfMonth) <= 6) and: [ each year = yr ] ] ]</lang>Output:Send value: 2012 to the above block to return an array: (27 January 2012 24 February 2012 30 March 2012 27 April 2012 25 May 2012 29 June 2012 27 July 2012 31 August 2012 28 September 2012 26 October 2012 30 November 2012 28 December 2012)SQL<lang SQL> select to_char( next_day( last_day( add_months( to_date(:yr||'01','yyyymm' ),level-1))-7,'Fri') ,'yyyy-mm-dd Dy') lastfridayfrom dual connect by level <= 12; </lang>LASTFRIDAY ----------------------- 2012-01-27 Fri 2012-02-24 Fri 2012-03-30 Fri 2012-04-27 Fri 2012-05-25 Fri 2012-06-29 Fri 2012-07-27 Fri 2012-08-31 Fri 2012-09-28 Fri 2012-10-26 Fri 2012-11-30 Fri 2012-12-28 Fri 12 rows selected.Stata<lang stata>program last_fridays args year clear qui set obs 12 gen day=dofm(mofd(mdy(_n,1,`year'))+1)-1 qui replace day=day-mod(dow(day)-5,7) format %td day list, noobs noheader sep(6) end last_fridays 2012+-----------+ | 27jan2012 | | 24feb2012 | | 30mar2012 | | 27apr2012 | | 25may2012 | | 29jun2012 | |-----------| | 27jul2012 | | 31aug2012 | | 28sep2012 | | 26oct2012 | | 30nov2012 | | 28dec2012 | +-----------+</lang>Swift<lang Swift> import Foundation func lastFridays(of year: Int) -> [Date] { let calendar = Calendar.current var dates = [Date]() for month in 2...13 { let lastDayOfMonth = DateComponents(calendar: calendar, year: year, month: month, day: 0, hour: 12) let date = calendar.date(from: lastDayOfMonth)! let isFriday = calendar.component(.weekday, from: date) == 6 if isFriday { dates.append(calendar.date(from: lastDayOfMonth)!) } else { let lastWeekofMonth = calendar.ordinality(of: .weekOfMonth, in: .month, for: date)! let lastWithFriday = lastWeekofMonth - (calendar.component(.weekday, from: date) > 6 ? 0 : 1) let lastFridayOfMonth = DateComponents(calendar: calendar, year: year, month: month - 1, hour: 12, weekday: 6, weekOfMonth: lastWithFriday) dates.append(calendar.date(from: lastFridayOfMonth)!) } } return dates } var dateFormatter = DateFormatter() dateFormatter.dateStyle = .short print(lastFridays(of: 2013).map(dateFormatter.string).joined(separator: "\n")) </lang>1/27/12 2/24/12 3/30/12 4/27/12 5/25/12 6/29/12 7/27/12 8/31/12 9/28/12 10/26/12 11/30/12 12/28/12Tcl<lang tcl>package require Tcl 8.5 set year [lindex $argv 0] foreach dm {02/1 03/1 04/1 05/1 06/1 07/1 08/1 09/1 10/1 11/1 12/1 12/32} {# The [clock scan] code is unhealthily clever; use it for our own evil purposes set t [clock scan "last friday" -base [clock scan $dm/$year -gmt 1] -gmt 1] # Print the interesting part puts [clock format $t -format "%Y-%m-%d" -gmt 1]}</lang> Sample execution:$ tclsh8.5 lastfri.tcl 2012 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28TUSCRIPT<lang tuscript> $$ MODE TUSCRIPT year=2012 LOOP month=1,12LOOP day=31,22,-1 dayofweek=DATE (number,day,month,year,nummer) IF (dayofweek==5) THEN PRINT year,"-",month,"-",day EXIT ENDIF ENDLOOPENDLOOP </lang>Output:2012-1-27 2012-2-24 2012-3-30 2012-4-27 2012-5-25 2012-6-29 2012-7-27 2012-8-31 2012-9-28 2012-10-26 2012-11-30 2012-12-28UNIX ShellUsing ncal. Will switch to Julian calender as ncal sees fit, and will not calculate past year 9999 (chances are you'll be too dead by then to worry about weekends anyway). <lang bash>#!/bin/sh if [ -z $1 ]; then exit 1; fiweed out multiple erros due to bad yearncal 1 $1 > /dev/null && \ for m in 01 02 03 04 05 06 07 08 09 10 11 12; do echo $1-$m-`ncal $m $1 | grep Fr | sed 's/.* $[0-9]$/\1/'` done</lang> For systems without ncal: <lang sh>#!/bin/shusage: last_fridays [ year]year=${1:-`date +%Y`} # default to current year month=1 while [ 12 -ge $month ]; do# Ensure 2 digits: if we try to strip off 2 characters but it still # looks the same, that means there was only 1 char, so we'll pad it. [ "$month" = "${month%??}" ] && month=0$monthcal $month $year | awk '{print $6}' | grep . | tail -1 \ | sed "s@^@$year-$month-@"# Strip leading zeros to avoid octal interpretation month=$(( 1 + ${month#0} ))done</lang> Using date --date from GNU date??? This code is not portable. <lang bash>#!/bin/shFree code, no limit work $Id: lastfridays,v 1.1 2011/11/10 00:48:16 gilles Exp gilles $usage : lastfridays 2012 # prints last fridays of months of year 2012debug=${debug:-false}debug=trueepoch_year_day() { #set -x x_epoch=`expr ${2:-0} '*' 86400 + 43200` date --date="${1:-1970}-01-01 UTC $x_epoch seconds" +%s } year_of_epoch() { date --date="1970-01-01 UTC ${1:-0} seconds" +%Y } day_of_epoch() { LC_ALL=C date --date="1970-01-01 UTC ${1:-0} seconds" +%A } date_of_epoch() { date --date="1970-01-01 UTC ${1:-0} seconds" "+%Y-%m-%d" } month_of_epoch() { date --date="1970-01-01 UTC ${1:-0} seconds" "+%m" } last_fridays() { year=${1:-2012}next_year=`expr $year + 1` $debug && echo "next_year $next_year"current_year=$year day=0 previous_month=01while test $current_year != $next_year; do$debug && echo "day $day"current_epoch=`epoch_year_day $year $day` $debug && echo "current_epoch $current_epoch"current_year=`year_of_epoch $current_epoch`current_day=`day_of_epoch $current_epoch` $debug && echo "current_day $current_day"test $current_day = 'Friday' && current_friday=`date_of_epoch $current_epoch` $debug && echo "current_friday $current_friday"current_month=`month_of_epoch $current_epoch` $debug && echo "current_month $current_month"# Change of month => previous friday is the last of month test "$previous_month" != "$current_month" \ && echo $previous_friday previous_month=$current_month previous_friday=$current_friday day=`expr $day + 1` done}mainlast_fridays ${1:-2012}</lang> Sample execution:lastfridays 2012 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28Visual FoxPro<lang vfp>!* OOP implementaionLOCAL lnYear As Integer, oCalc As fricalc CLEAR lnYear = VAL(INPUTBOX("Year", "Year")) oCalc = NEWOBJECT("fricalc") oCalc.LastFriday(lnYear) DEFINE CLASS fricalc As Session DataSession = 2 && Private PROCEDURE Init!* These date settings are private to this classSET DATE YMD SET CENTURY ON SET MARK TO "-" ENDPROC FUNCTION LastFriday(tnYear As Integer) As VOID LOCAL i As Integer, ldDate As Date CLEAR ? "Last Fridays in the year " + TRANSFORM(tnYear) FOR i = 1 TO 12 ldDate = DATE(tnYear, i, 1) && 1st of month ldDate = GOMONTH(ldDate, 1) - 1 && last day of month *!* Use the built in function to return the day of the week *!* 6 is Friday DO WHILE DOW(ldDate) # 6 ldDate = ldDate - 1 ENDDO ? ldDate ENDFOR ENDFUNC ENDDEFINE </lang>WrenLibrary: Wren-date<lang ecmascript>import "os" for Process import "/date" for Date var args = Process.arguments if (args.count != 1) {Fiber.abort("Please pass just the year to be processed.")} var year = Num.fromString(args[0]) System.print("The dates of the last Fridays in the month for %(year) are:") Date.default = Date.isoDate for (m in 1..12) {var d = Date.monthLength(year, m) var dt = Date.new(year, m, d) var wd = dt.dayOfWeek if (wd == 5) { System.print(dt) } else if (wd > 5) { System.print(dt.addDays(-wd + 5)) } else { System.print(dt.addDays(-wd - 2)) }}</lang>Output:$ wren last_friday.wren 2012 The dates of the last Fridays in the month for 2012 are: 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28 $ wren last_friday.wren 2020 The dates of the last Fridays in the month for 2020 are: 2020-01-31 2020-02-28 2020-03-27 2020-04-24 2020-05-29 2020-06-26 2020-07-31 2020-08-28 2020-09-25 2020-10-30 2020-11-27 2020-12-25XPL0<lang XPL0>include c:\cxpl\codes; \intrinsic 'code' declarations func WeekDay(Year, Month, Day); \Return day of week (0=Sun, 1=Mon ... 6=Sat) int Year, Month, Day; \works for years from 1583 onward [if Month<=2 then [Month:= Month+12; Year:= Year-1]; return rem((Day-1 + (Month+1)*26/10 + Year + Year/4 + Year/100*6 + Year/400)/7); ]; int Year, Month, LastDay, WD; [Year:= IntIn(8); \from command line for Month:= 1 to 12 do[LastDay:= WeekDay(Year, Month+1, 1) - WeekDay(Year, Month, 28); if LastDay < 0 then LastDay:= LastDay + 7; LastDay:= LastDay + 27; \ = number of days in Month WD:= WeekDay(Year, Month, LastDay); WD:= WD - 5; if WD < 0 then WD:= WD + 7; LastDay:= LastDay - WD; IntOut(0, Year); ChOut(0, ^-); if Month < 10 then ChOut(0, ^0); IntOut(0, Month); ChOut(0, ^-); IntOut(0, LastDay); CrLf(0); ];]</lang>Output:2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28zklGregorian calendar <lang zkl>var [const] D=Time.Date; fcn lastDay(y,d){[1..12].pump(List,'wrap(m){ // 12 months, closure for y & d [D.daysInMonth(y,m)..1,-1].pump(Void,'wrap(_d){ // work backwards D.weekDay(y,m,_d) : if (_==d) return(Void.Stop,D.toYMDString(y,m,_d)) }) })} lastDay(2012,D.Friday).concat("\n").println();</lang> For each month in year y, count back from the last day in the month until a Friday is found and print that date. A pump is a loop over a sequence and Void.Stop stops the pump with a value. The first parameter to a pump is the sink. All the imperative loop constructs are available but I didn't feel like using them. A wrap is a function closure over unknown values in the function, necessary because functions are not lexically scoped.Output:2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28