Calendar

From Rosetta Code
Task
Calendar
You are encouraged to solve this task according to the task description, using any language you may know.

Create a routine that will generate a text calendar for any year. Test the calendar by generating a calendar for the year 1969, on a device of the time. Choose one of the following devices:

  • A line printer with a width of 132 characters.
  • An IBM 3278 model 4 terminal (80×43 display with accented characters). Target formatting the months of the year to fit nicely across the 80 character width screen. Restrict number of lines in test output to 43.

(Ideally, the program will generate well-formatted calendars for any page width from 20 characters up.)

Kudos (κῦδος) for routines that also correctly transition from Julian to Gregorian calendar in September 1752.

This task is inspired by Real Programmers Don't Use PASCAL by Ed Post, Datamation, volume 29 number 7, July 1983.

THE REAL PROGRAMMER'S NATURAL HABITAT
"Taped to the wall is a line-printer Snoopy calender for the year 1969."

For further Kudos see task CALENDAR, where all code is to be in UPPERCASE.

For economy of size, do not actually include Snoopy generation in either the code or the output, instead just output a place-holder.

Ada

Specification of a "Printable_Calendar" package (printable_calendar.ads):

<lang Ada>with Ada.Calendar.Formatting;

package Printable_Calendar is

  subtype String20 is String(1 .. 20);
  type Month_Rep_Type is array (Ada.Calendar.Month_Number) of String20;
  type Description is record
     Weekday_Rep: String20;
     Month_Rep: Month_Rep_Type;
  end record;
  -- for internationalization, you only need to define a new description
  Default_Description: constant Description :=
    (Weekday_Rep =>
      "Mo Tu We Th Fr Sa So",
     Month_Rep   =>
     ("      January       ", "      February      ", "       March        ",
      "       April        ", "        May         ", "        June        ",
      "        July        ", "       August       ", "      September     ",
      "       October      ", "      November      ", "      December      "));
  type Calendar (<>) is tagged private;
  -- Initialize a calendar for devices with 80- or 132-characters per row
  function Init_80(Des: Description := Default_Description) return Calendar;
  function Init_132(Des: Description := Default_Description) return Calendar;
  -- the following procedures output to standard IO; override if neccessary
  procedure New_Line(Cal: Calendar);
  procedure Put_String(Cal: Calendar; S: String);
  -- the following procedures do the real stuff
  procedure Print_Line_Centered(Cal: Calendar'Class; Line: String);
  procedure Print(Cal: Calendar'Class;
                  Year:  Ada.Calendar.Year_Number;
                  Year_String: String); -- this is the main Thing

private

     type Calendar is tagged record
     Columns, Rows, Space_Between_Columns: Positive;
     Left_Space: Natural;
     Weekday_Rep: String20;
     Month_Rep: Month_Rep_Type;
  end record;

end Printable_Calendar;</lang>

Next the implementation (printable_calendar.ads):

<lang Ada>with Ada.Text_IO;

package body Printable_Calendar is

  use Ada.Calendar;
  package F renames Ada.Calendar.Formatting;
  function Days_Per_Month(Year: Year_Number; Month: Month_Number)
                         return Day_Number is
  begin
     case Month is
        when 1 | 3 | 5 | 7 | 8 | 10 | 12 => return 31;
        when 4 | 6 | 9 | 11              => return 30;
        when 2 =>
           if Year mod 4 /= 0 then
              return 28;
           elsif Year mod 100 /= 0 then
              return 29;
           elsif Year mod 400 /= 0 then
              return 28;
           else
              return 29;
           end if;
     end case;
  end Days_Per_Month;
  type Full_Month_Rep is array (1 .. 6) of String20;
  function Generate_Printable_Month (Y: Ada.Calendar.Year_Number;
                                     M: Ada.Calendar.Month_Number)
                                    return Full_Month_Rep is
     X: Full_Month_Rep := (others => "                    ");
     -- If X=Generate_Printable_Month(2011, 01), the result could be
     --  "       January      ", -- Month_Rep(01)
     --  "Mo Tu We Th Fr Sa Su"  -- Weekday_Rep
     --  "                1  2"  -- X(1)
     --  " 3  4  5  6  7  8  9"  -- X(2)
     --  "10 11 12 13 14 15 16"  -- X(3)
     --  "17 18 19 20 21 22 23"  -- X(4)
     --  "24 25 26 27 28 29 30"  -- X(5)
     --  "31                  "  -- X(6)
     Row:       Integer range 1 .. 6  := 1;
     Day_Index: constant array(F.Day_Name) of Positive
       := (1, 4, 7, 10, 13, 16, 19);
  begin
     for I in 1 .. Days_Per_Month(Y, M) loop
        declare
          Weekday: constant F.Day_Name    := F.Day_Of_Week(F.Time_Of(Y, M, I));
          Pos: constant Positive          := Day_Index(Weekday);
          Cleartext_Name: constant String := Day_Number'Image(I);
          L: constant Positive            := Cleartext_Name'Last;
        begin
           X(Row)(Pos .. Pos+1) := Cleartext_Name(L-1 .. L);
           if F."="(Weekday, F.Sunday) then
              Row := Row + 1;
           end if;
        end;
     end loop;
     return X;
  end Generate_Printable_Month;


  procedure Print(Cal: Calendar'class;
                  Year:  Ada.Calendar.Year_Number;
                  Year_String: String) is
     The_Month: Month_Number := Month_Number'First;
     procedure Write_Space(Length: Natural) is
     begin
        for I in 1 .. Length loop
           Cal.Put_String(" ");
        end loop;
     end Write_Space;
     Year_Rep: array(Month_Number) of Full_Month_Rep;
  begin
     -- print the year
     Cal.Print_Line_Centered(Year_String);
     -- generate a printable form for all the months
     for Month in Month_Number loop
        Year_Rep(Month) := Generate_Printable_Month(Year, Month);
     end loop;
     begin
        while True loop
           -- new line
           Cal.New_Line;
           -- write month names
           Write_Space(Cal.Left_Space);
           for Month in The_Month .. The_Month+Cal.Columns-2 loop
              Cal.Put_String(Cal.Month_Rep(Month));
              Write_Space(Cal.Space_Between_Columns);
           end loop;
           Cal.Put_String(Cal.Month_Rep(The_Month+Cal.Columns-1));
           Cal.New_Line;
           -- write "Mo Tu .. So" - or whatever is defined by Weekday_Rep
           Write_Space(Cal.Left_Space);
           for Month in The_Month .. The_Month+Cal.Columns-2 loop
              Cal.Put_String(Cal.Weekday_Rep);
              Write_Space(Cal.Space_Between_Columns);
           end loop;
           Cal.Put_String(Cal.Weekday_Rep);
           Cal.New_Line;
           -- write the dates
           for I in 1 .. 6 loop
              Write_Space(Cal.Left_Space);
              for Month in The_Month .. The_Month+Cal.Columns-2 loop
                 Cal.Put_String(Year_Rep(Month)(I));
                 Write_Space(Cal.Space_Between_Columns);
              end loop;
           Cal.Put_String(Year_Rep(The_Month+Cal.Columns-1)(I));
           Cal.New_Line;
           end loop;
           The_Month := The_Month + Cal.Columns;
           -- this will eventually raise Constraint_Error to terminate the loop
        end loop;
     exception
        when Constraint_Error => null;
     end;
  end Print;
  procedure New_Line(Cal: Calendar) is
  begin
     Ada.Text_IO.New_Line;
  end New_Line;
  procedure Put_String(Cal: Calendar; S: String) is
  begin
     Ada.Text_IO.Put(S);
  end Put_String;
  procedure Print_Line_Centered(Cal: Calendar'Class; Line: String) is
     Width : constant Positive := Cal.Columns*20
       + (Cal.Columns-1)*Cal.Space_Between_Columns
       + Cal.Left_Space;
  begin
     if Line'Length    >= Width-1 then
        Cal.Put_String(Line);
        Cal.New_Line;
     else
        Print_Line_Centered(Cal, " " & Line & " ");
     end if;
  end Print_Line_Centered;
  function Init_80(Des: Description := Default_Description) return Calendar is
     X: Calendar:=
       (Columns => 3, Rows => 4, Space_Between_Columns => 4,
        Left_Space => 1,
        Weekday_Rep =>  Des.Weekday_Rep,
        Month_Rep   =>  Des.Month_Rep
       );
  begin
     return X;
  end Init_80;
  function Init_132(Des: Description := Default_Description) return Calendar is
     X: Calendar:=
       (Columns => 6, Rows => 2, Space_Between_Columns => 2,
        Left_Space => 1,
        Weekday_Rep =>  Des.Weekday_Rep,
        Month_Rep   =>  Des.Month_Rep
       );
  begin
     return X;
  end Init_132;

end Printable_Calendar;</lang>

Now, the main program is really simple:

<lang Ada>with Printable_Calendar;

procedure Cal is

  C: Printable_Calendar.Calendar := Printable_Calendar.Init_80;

begin

  C.Print_Line_Centered("[reserved for Snoopy]");
  C.New_Line;
  C.Print(1969, "Nineteen-Sixty-Nine");

end Cal;</lang>

Here is the output:

                        [reserved for Snoopy]                        

                         Nineteen-Sixty-Nine                         

       January                 February                 March        
 Mo Tu We Th Fr Sa So    Mo Tu We Th Fr Sa So    Mo Tu We Th Fr Sa So
        1  2  3  4  5                    1  2                    1  2
  6  7  8  9 10 11 12     3  4  5  6  7  8  9     3  4  5  6  7  8  9
 13 14 15 16 17 18 19    10 11 12 13 14 15 16    10 11 12 13 14 15 16
 20 21 22 23 24 25 26    17 18 19 20 21 22 23    17 18 19 20 21 22 23
 27 28 29 30 31          24 25 26 27 28          24 25 26 27 28 29 30
                                                 31                  

        April                    May                     June        
 Mo Tu We Th Fr Sa So    Mo Tu We Th Fr Sa So    Mo Tu We Th Fr Sa So
     1  2  3  4  5  6              1  2  3  4                       1
  7  8  9 10 11 12 13     5  6  7  8  9 10 11     2  3  4  5  6  7  8
 14 15 16 17 18 19 20    12 13 14 15 16 17 18     9 10 11 12 13 14 15
 21 22 23 24 25 26 27    19 20 21 22 23 24 25    16 17 18 19 20 21 22
 28 29 30                26 27 28 29 30 31       23 24 25 26 27 28 29
                                                 30                  

         July                   August                 September     
 Mo Tu We Th Fr Sa So    Mo Tu We Th Fr Sa So    Mo Tu We Th Fr Sa So
     1  2  3  4  5  6                 1  2  3     1  2  3  4  5  6  7
  7  8  9 10 11 12 13     4  5  6  7  8  9 10     8  9 10 11 12 13 14
 14 15 16 17 18 19 20    11 12 13 14 15 16 17    15 16 17 18 19 20 21
 21 22 23 24 25 26 27    18 19 20 21 22 23 24    22 23 24 25 26 27 28
 28 29 30 31             25 26 27 28 29 30 31    29 30               
                                                                     

        October                November                December      
 Mo Tu We Th Fr Sa So    Mo Tu We Th Fr Sa So    Mo Tu We Th Fr Sa So
        1  2  3  4  5                    1  2     1  2  3  4  5  6  7
  6  7  8  9 10 11 12     3  4  5  6  7  8  9     8  9 10 11 12 13 14
 13 14 15 16 17 18 19    10 11 12 13 14 15 16    15 16 17 18 19 20 21
 20 21 22 23 24 25 26    17 18 19 20 21 22 23    22 23 24 25 26 27 28
 27 28 29 30 31          24 25 26 27 28 29 30    29 30 31  


To get a 132-character-wide output, you just have to replace "Init_80" by "Init_132" in the main program.

ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny.

<lang algol68>#!/usr/local/bin/a68g --script #

PROC print calendar = (INT year, page width)VOID: (

 []STRING month names = (
     "January","February","March","April","May","June",
     "July","August","September","October","November","December"),
   weekday names = ("Su","Mo","Tu","We","Th","Fr","Sa");
 FORMAT weekday fmt = $g,n(UPB weekday names - LWB weekday names)(" "g)$;
 # Juggle the calendar format to fit the printer/screen width #
 INT day width = UPB weekday names[1], day gap=1;
 INT month width = (day width+day gap) * UPB weekday names-1;
 INT month heading lines = 2;
 INT month lines = (31 OVER UPB weekday names+month heading lines+2); # +2 for head/tail weeks #
 INT year cols = (page width+1) OVER (month width+1);
 INT year rows = (UPB month names-1)OVER year cols + 1;
 INT month gap = (page width - year cols*month width + 1)OVER year cols;
 INT year width = year cols*(month width+month gap)-month gap;
 INT year lines = year rows*month lines;
 MODE MONTHBOX = [month lines, month width]CHAR;
 MODE YEARBOX  = [year  lines, year  width]CHAR;
 INT week start = 1; # Sunday #
 PROC days in month = (INT year, month)INT:
   CASE month IN 31,
     IF year MOD 4 EQ 0 AND year MOD 100 NE 0 OR year MOD 400 EQ 0 THEN 29 ELSE 28 FI,
     31, 30, 31, 30, 31, 31, 30, 31, 30, 31
   ESAC;
 PROC day of week = (INT year, month, day)INT: (
   # Day of the week by Zeller’s Congruence algorithm from 1887 #
   INT y := year, m := month, d := day, c;
   IF m <= 2 THEN m +:= 12; y -:= 1 FI;
   c := y OVER 100;
   y %*:= 100;
   (d - 1 + ((m + 1) * 26) OVER 10 + y + y OVER 4 + c OVER 4 - 2 * c) MOD 7
 );
 MODE SIMPLEOUT = UNION(STRING, []STRING, INT);
 PROC cputf = (REF[]CHAR out, FORMAT fmt, SIMPLEOUT argv)VOID:(
   FILE f; STRING s; associate(f,s);
   putf(f, (fmt, argv));
   out[:UPB s]:=s;
   close(f)
 );
 PROC month repr = (INT year, month)MONTHBOX:(
   MONTHBOX month box; FOR line TO UPB month box DO month box[line,]:=" "* 2 UPB month box OD;
   STRING month name = month names[month];
 # center the title #
   cputf(month box[1,(month width - UPB month name ) OVER 2+1:], $g$, month name);
   cputf(month box[2,], weekday fmt, weekday names);
   INT first day := day of week(year, month, 1);
   FOR day TO days in month(year, month) DO
     INT line = (day+first day-week start) OVER UPB weekday names + month heading lines + 1;
     INT char =((day+first day-week start) MOD UPB weekday names)*(day width+day gap) + 1;
     cputf(month box[line,char:char+day width-1],$g(-day width)$, day)
   OD;
   month box
 );
 PROC year repr = (INT year)YEARBOX:(
   YEARBOX year box;
   FOR line TO UPB year box DO year box[line,]:=" "* 2 UPB year box OD;
   FOR month row FROM 0 TO year rows-1 DO
     FOR month col FROM 0 TO year cols-1 DO
       INT month = month row * year cols + month col + 1;
       IF month > UPB month names THEN
         done
       ELSE
         INT month col width = month width+month gap;
         year box[
           month row*month lines+1 : (month row+1)*month lines,
           month col*month col width+1 : (month col+1)*month col width-month gap
         ] := month repr(year, month)
       FI
     OD
   OD;
   done: year box
 );
 INT center = (year cols*(month width+month gap) - month gap - 1) OVER 2;
 INT indent = (page width - year width) OVER 2;
 printf((
   $n(indent + center - 9)k  g l$, "[Insert Snoopy here]",
   $n(indent + center - 1)k 4d l$, year, $l$,
   $n(indent)k n(year width)(g)  l$, year repr(year)
 ))

);

main: ( CO inspired by http://www.ee.ryerson.ca/~elf/hack/realmen.html

          Real Programmers Don't Use PASCAL - Ed Post
           Datamation, volume 29 number 7, July 1983
             THE REAL PROGRAMMER'S NATURAL HABITAT

"Taped to the wall is a line-printer Snoopy calender for the year 1969." CO

 INT mankind stepped on the moon = 1969,
     line printer width = 80; # as at 1969! #
 print calendar(mankind stepped on the moon, line printer width)

)</lang> Output:

                             [Insert Snoopy here]
                                     1969

        January                    February                    March        
  Su Mo Tu We Th Fr Sa       Su Mo Tu We Th Fr Sa       Su Mo Tu We Th Fr Sa
            1  2  3  4                          1                          1
   5  6  7  8  9 10 11        2  3  4  5  6  7  8        2  3  4  5  6  7  8
  12 13 14 15 16 17 18        9 10 11 12 13 14 15        9 10 11 12 13 14 15
  19 20 21 22 23 24 25       16 17 18 19 20 21 22       16 17 18 19 20 21 22
  26 27 28 29 30 31          23 24 25 26 27 28          23 24 25 26 27 28 29
                                                        30 31               
         April                       May                        June        
  Su Mo Tu We Th Fr Sa       Su Mo Tu We Th Fr Sa       Su Mo Tu We Th Fr Sa
         1  2  3  4  5                    1  2  3        1  2  3  4  5  6  7
   6  7  8  9 10 11 12        4  5  6  7  8  9 10        8  9 10 11 12 13 14
  13 14 15 16 17 18 19       11 12 13 14 15 16 17       15 16 17 18 19 20 21
  20 21 22 23 24 25 26       18 19 20 21 22 23 24       22 23 24 25 26 27 28
  27 28 29 30                25 26 27 28 29 30 31       29 30               
                                                                            
          July                      August                   September      
  Su Mo Tu We Th Fr Sa       Su Mo Tu We Th Fr Sa       Su Mo Tu We Th Fr Sa
         1  2  3  4  5                       1  2           1  2  3  4  5  6
   6  7  8  9 10 11 12        3  4  5  6  7  8  9        7  8  9 10 11 12 13
  13 14 15 16 17 18 19       10 11 12 13 14 15 16       14 15 16 17 18 19 20
  20 21 22 23 24 25 26       17 18 19 20 21 22 23       21 22 23 24 25 26 27
  27 28 29 30 31             24 25 26 27 28 29 30       28 29 30            
                             31                                             
        October                    November                   December      
  Su Mo Tu We Th Fr Sa       Su Mo Tu We Th Fr Sa       Su Mo Tu We Th Fr Sa
            1  2  3  4                          1           1  2  3  4  5  6
   5  6  7  8  9 10 11        2  3  4  5  6  7  8        7  8  9 10 11 12 13
  12 13 14 15 16 17 18        9 10 11 12 13 14 15       14 15 16 17 18 19 20
  19 20 21 22 23 24 25       16 17 18 19 20 21 22       21 22 23 24 25 26 27
  26 27 28 29 30 31          23 24 25 26 27 28 29       28 29 30 31         
                             30                                             

C

With arbitrary display width (>= 20 though) and auto spacing. <lang C>#define _XOPEN_SOURCE

  1. include <time.h>
  2. include <stdio.h>
  3. include <stdlib.h>
  4. include <string.h>

int width = 80, year = 1969; int cols, lead, gap;

char *wdays[] = { "Su", "Mo", "Tu", "We", "Th", "Fr", "Sa" }; struct months { char *name; int days, start_wday, at; } months[12] = { { "January", 31, 0, 0 }, { "Februray", 28, 0, 0 }, { "March", 31, 0, 0 }, { "April", 30, 0, 0 }, { "May", 31, 0, 0 }, { "June", 30, 0, 0 }, { "July", 31, 0, 0 }, { "August", 31, 0, 0 }, { "September", 30, 0, 0 }, { "October", 31, 0, 0 }, { "November", 30, 0, 0 }, { "December", 31, 0, 0 } };

void space(int n) { while (n-- > 0) putchar(' '); }

void init_months() { char buf[128]; struct tm tm; int i;

if ((!(year % 4) && (year % 100)) || !(year % 400)) months[1].days = 29; sprintf(buf, "%d 1 1", year); strptime(buf, "%Y %m %d", &tm); months[0].start_wday = tm.tm_wday; for (i = 1; i < 12; i++) months[i].start_wday = (months[i-1].start_wday + months[i-1].days) % 7; cols = (width + 2) / 22; while (12 % cols) cols--; gap = cols - 1 ? (width - 20 * cols) / (cols - 1) : 0; if (gap > 4) gap = 4; lead = (width - (20 + gap) * cols + gap + 1) / 2; }

void print_row(int row) { int c, i, from = row * cols, to = from + cols; space(lead); for (c = from; c < to; c++) { i = strlen(months[c].name); space((20 - i)/2); printf("%s", months[c].name); space(20 - i - (20 - i)/2 + ((c == to - 1) ? 0 : gap)); } putchar('\n');

space(lead); for (c = from; c < to; c++) { for (i = 0; i < 7; i++) printf("%s%s", wdays[i], i == 6 ? "" : " "); if (c < to - 1) space(gap); else putchar('\n'); }

while (1) { for (c = from; c < to; c++) if (months[c].at < months[c].days) break; if (c == to) break;

space(lead); for (c = from; c < to; c++) { for (i = 0; i < months[c].start_wday; i++) space(3); while(i++ < 7 && months[c].at < months[c].days) { printf("%2d", ++months[c].at); if (i < 7 || c < to - 1) putchar(' '); } while (i++ <= 7 && c < to - 1) space(3); if (c < to - 1) space(gap - 1); months[c].start_wday = 0; } putchar('\n'); } putchar('\n'); }

void print_year() { int row; char buf[32]; sprintf(buf, "%d", year); space((width - strlen(buf)) / 2); printf("%s\n\n", buf); for (row = 0; row * cols < 12; row++) print_row(row); }

int main(int c, char **v) { int i, year_set = 0; for (i = 1; i < c; i++) { if (!strcmp(v[i], "-w")) { if (++i == c || (width = atoi(v[i])) < 20) goto bail; } else if (!year_set) { if (!sscanf(v[i], "%d", &year)) year = 1969; year_set = 1; } else goto bail; }

init_months(); print_year(); return 0;

bail: fprintf(stderr, "bad args\nUsage: %s year [-w width (>= 20)]\n", v[0]); exit(1); }</lang>



C#

An attempt to abuse the DateTime class for all static information. In the event that the number of days and months changes, so long as the DateTime class is updated accordingly, this should still print properly.

<lang csharp>

using System; using System.Collections.Generic; using System.Linq; using System.Text;

namespace CalendarStuff {

   class Program
   {
       static void Main(string[] args)
       {
           Console.WindowHeight = 46;
           StringBuilder sb = new StringBuilder();
           sb.Append(buildMonths(new DateTime(1969, 1, 1)));
           Console.Write(sb.ToString());
           Console.Read(); 
       }
       private static string buildMonths(DateTime date)
       {
           StringBuilder sb = new StringBuilder();
           sb.AppendLine(center("[Snoop]", 24 * 3));
           sb.AppendLine();
           sb.AppendLine(center(date.Year.ToString(), 24 * 3));
           List<DateTime> dts = new List<DateTime>();
           while (true)
           {
               dts.Add(date);
               if (date.Year != ((date = date.AddMonths(1)).Year))
               {
                   break;
               }
           }
           var jd = dts.Select(a => buildMonth(a).GetEnumerator()).ToArray();
           
           int sCur=0;
           while (sCur<dts.Count)
           {
               sb.AppendLine();
               int curMonth=0; 
               var j = jd.Where(a => curMonth++ >= sCur && curMonth - 1 < sCur + 3).ToArray(); //grab the next 3
               sCur += j.Length; 
               bool breakOut = false;
               while (!breakOut)
               {
                   int inj = 1;
                   foreach (var cd in j)
                   {
                       if (cd.MoveNext())
                       {
                           sb.Append((cd.Current.Length == 21 ? cd.Current : cd.Current.PadRight(21, ' ')) + "     ");
                       }
                       else
                       {
                           sb.Append("".PadRight(21, ' ') + "     ");
                           breakOut = true;
                       }
                       if (inj++ % 3 == 0) sb.AppendLine();
                   }
               }
           }
           return sb.ToString();
       }


       private static IEnumerable<string> buildMonth(DateTime date)
       {
           yield return center(date.ToString("MMMM"),7*3);
           var j = DateTime.DaysInMonth(date.Year, date.Month);
           yield return Enum.GetNames(typeof(DayOfWeek)).Aggregate("", (current, result) => current + (result.Substring(0, 2).ToUpper() + " "));
           string cur = "";
           int total = 0;
           foreach (var day in Enumerable.Range(-((int)date.DayOfWeek),j))
           {
               cur += (day < 0 ? "  " : ((day < 9 ? " " : "") + (day + 1))) +" ";
               if (total++ > 0 && (total ) % 7 == 0)
               {
                   yield return cur;
                   cur = "";
               }
           }
           yield return cur;
       }
       private static string center(string s, int len)
       {
           return (s.PadLeft((len - s.Length) / 2 + s.Length, ' ').PadRight((len), ' '));
       } 
   }

}

</lang>

D

Works with: D version 2

<lang d>import std.stdio, std.datetime, std.string, std.exception, std.conv;

void main() {

   printCalendar(1969, 3);

}

void printCalendar(in int year, in int cols) {

   enforce(1 <= cols && cols <= 12);
   
   auto rows = 12 / cols + (12 % cols != 0); 
   auto date = Date(year, 1, 1);
   auto offs = cast(int)date.dayOfWeek();
   auto monthNames = "January February March April May June "
   "July August September October November December".split(" "); 
       
   string[8][12] mons;
   foreach (m; 0 .. 12) {
       mons[m][0] = monthNames[m].center(21);
       mons[m][1] = " Su Mo Tu We Th Fr Sa";
       int eom = date.endOfMonthDay();
       foreach (d; 1 .. 43) {
           auto day = d > offs && d <= offs + eom; 
           auto str = day ? format(" %2s", d-offs) : "   ";
           mons[m][2 + (d - 1) / 7] ~= str;
       }
       offs = (offs + eom) % 7;
       date.add!q{months}(1);
   }
   writeln("[Snoopy Picture]".center(cols * 24 + 4));
   writeln(to!string(year).center(cols * 24 + 4), "\n");
   foreach (r; 0 .. rows) {
       auto s = new string[8];
       foreach (c; 0 .. cols) {
           if (r * cols + c > 11) break;
           foreach (i, line; mons[r * cols + c]) 
               s[i] ~= format("   %s", line);
       }
       writeln(join(s, "\n"), "\n");
   }

}</lang>

                              [Snoopy Picture]
                                    1969

          January                February                  March
    Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa
              1  2  3  4                       1                       1
     5  6  7  8  9 10 11     2  3  4  5  6  7  8     2  3  4  5  6  7  8
    12 13 14 15 16 17 18     9 10 11 12 13 14 15     9 10 11 12 13 14 15
    19 20 21 22 23 24 25    16 17 18 19 20 21 22    16 17 18 19 20 21 22
    26 27 28 29 30 31       23 24 25 26 27 28       23 24 25 26 27 28 29
                                                    30 31

           April                    May                    June
    Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa
           1  2  3  4  5                 1  2  3     1  2  3  4  5  6  7
     6  7  8  9 10 11 12     4  5  6  7  8  9 10     8  9 10 11 12 13 14
    13 14 15 16 17 18 19    11 12 13 14 15 16 17    15 16 17 18 19 20 21
    20 21 22 23 24 25 26    18 19 20 21 22 23 24    22 23 24 25 26 27 28
    27 28 29 30             25 26 27 28 29 30 31    29 30


           July                   August                 September
    Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa
           1  2  3  4  5                    1  2        1  2  3  4  5  6
     6  7  8  9 10 11 12     3  4  5  6  7  8  9     7  8  9 10 11 12 13
    13 14 15 16 17 18 19    10 11 12 13 14 15 16    14 15 16 17 18 19 20
    20 21 22 23 24 25 26    17 18 19 20 21 22 23    21 22 23 24 25 26 27
    27 28 29 30 31          24 25 26 27 28 29 30    28 29 30
                            31

          October                November                December
    Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa
              1  2  3  4                       1        1  2  3  4  5  6
     5  6  7  8  9 10 11     2  3  4  5  6  7  8     7  8  9 10 11 12 13
    12 13 14 15 16 17 18     9 10 11 12 13 14 15    14 15 16 17 18 19 20
    19 20 21 22 23 24 25    16 17 18 19 20 21 22    21 22 23 24 25 26 27
    26 27 28 29 30 31       23 24 25 26 27 28 29    28 29 30 31
                            30

GUISS

In Graphical User Interface Support Script, we utilize applications that are already written. So for this task, we shall just display the calendar that sets the system clock.

<lang guiss>Rightclick:Clock,Adjust Date and Time,Button:Cancel</lang>

Icon and Unicon

The procedures printCalendar handles formatting of large components and uses co-expressions to keep the formatting of week elements in each column synchronized. The procedure CalendarFormatWeek is a generator that returns heading elements, alignment spacing, and individual days. <lang Icon>procedure main(A) printCalendar(\A[1]|1969) end

procedure printCalendar(year) #: Print a 3 column x 80 char calendar

  cols := 3                                        # fixed width 
  mons := []                                       # table of months
  "January February March April May June " || 
  "July August September October November December " ?
         while put(mons, tab(find(" "))) do move(1)    
  write(center("[Snoopy Picture]",cols * 24 + 4))  # mandatory ..
  write(center(year,cols * 24 + 4), "\n")          # ... headers
  
  M := list(cols)	                               # coexpr container               
  every  mon := 0 to 9 by cols do {                # go through months by cols
     writes("    ")
     every i := 1 to cols do {
        writes(center(mons[mon+i],24))             # header months
        M[i] := create CalendarFormatWeek(1969,mon + i)  # formatting coexpr 
        }
     write()
     every 1 to 7 do {                             # 1 to max rows                   
        every c := 1 to cols do {                  # for each column
           writes("    ")
           every 1 to 7 do writes(right(@M[c],3))  # each row day element 
           }
        write()
        }
     }

end

link datetime

procedure CalendarFormatWeek(year,m) #: Format Week for Calendar static D initial D := [31,28,31,30,31,30,31,31,30,31,30,31]

every suspend "Su"|"Mo"|"Tu"|"We"|"Th"|"Fr"|"Sa" # header every 1 to (d := (julian(m,1,year)+1)%7) do suspend "" # lead day alignment every suspend 1 to D[m] do d +:= 1 # days if m = 2 & IsLeapYear(year) then suspend (d +:= 1, 29) # LY adjustment every d to (6*7) do suspend "" # trailer alignment end</lang>

datetime.icn provides julian and IsLeapYear

Output:

                              [Snoopy Picture]
                                    1969

            January                 February                 March
     Su Mo Tu We Th Fr Sa     Su Mo Tu We Th Fr Sa     Su Mo Tu We Th Fr Sa
               1  2  3  4                        1                        1
      5  6  7  8  9 10 11      2  3  4  5  6  7  8      2  3  4  5  6  7  8
     12 13 14 15 16 17 18      9 10 11 12 13 14 15      9 10 11 12 13 14 15
     19 20 21 22 23 24 25     16 17 18 19 20 21 22     16 17 18 19 20 21 22
     26 27 28 29 30 31        23 24 25 26 27 28        23 24 25 26 27 28 29
                                                       30 31
             April                    May                     June
     Su Mo Tu We Th Fr Sa     Su Mo Tu We Th Fr Sa     Su Mo Tu We Th Fr Sa
            1  2  3  4  5                  1  2  3      1  2  3  4  5  6  7
      6  7  8  9 10 11 12      4  5  6  7  8  9 10      8  9 10 11 12 13 14
     13 14 15 16 17 18 19     11 12 13 14 15 16 17     15 16 17 18 19 20 21
     20 21 22 23 24 25 26     18 19 20 21 22 23 24     22 23 24 25 26 27 28
     27 28 29 30              25 26 27 28 29 30 31     29 30

              July                   August                September
     Su Mo Tu We Th Fr Sa     Su Mo Tu We Th Fr Sa     Su Mo Tu We Th Fr Sa
            1  2  3  4  5                     1  2         1  2  3  4  5  6
      6  7  8  9 10 11 12      3  4  5  6  7  8  9      7  8  9 10 11 12 13
     13 14 15 16 17 18 19     10 11 12 13 14 15 16     14 15 16 17 18 19 20
     20 21 22 23 24 25 26     17 18 19 20 21 22 23     21 22 23 24 25 26 27
     27 28 29 30 31           24 25 26 27 28 29 30     28 29 30
                              31
            October                 November                December
     Su Mo Tu We Th Fr Sa     Su Mo Tu We Th Fr Sa     Su Mo Tu We Th Fr Sa
               1  2  3  4                        1         1  2  3  4  5  6
      5  6  7  8  9 10 11      2  3  4  5  6  7  8      7  8  9 10 11 12 13
     12 13 14 15 16 17 18      9 10 11 12 13 14 15     14 15 16 17 18 19 20
     19 20 21 22 23 24 25     16 17 18 19 20 21 22     21 22 23 24 25 26 27
     26 27 28 29 30 31        23 24 25 26 27 28 29     28 29 30 31
                              30

J

Solution: <lang j>require 'dates format' NB. J6.x require 'dates general/misc/format' NB. J7.x calBody=: (1 1 }. _1 _1 }. ":)@(-@(<.@%&22)@[ ]\ calendar@]) calTitle=: (<: - 22&|)@[ center '[Insert Snoopy here]' , ,:~ ":@] formatCalendar=: calTitle , calBody</lang> Example use: <lang j> 80 formatCalendar 1969

                     [Insert Snoopy here]                       
                             1969                               
                                                                
        Jan         │         Feb         │         Mar         
Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa
          1  2  3  4│                    1│                    1
 5  6  7  8  9 10 11│  2  3  4  5  6  7  8│  2  3  4  5  6  7  8
12 13 14 15 16 17 18│  9 10 11 12 13 14 15│  9 10 11 12 13 14 15
19 20 21 22 23 24 25│ 16 17 18 19 20 21 22│ 16 17 18 19 20 21 22
26 27 28 29 30 31   │ 23 24 25 26 27 28   │ 23 24 25 26 27 28 29
                    │                     │ 30 31               

─────────────────────┼─────────────────────┼─────────────────────

        Apr         │         May         │         Jun         
Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa
       1  2  3  4  5│              1  2  3│  1  2  3  4  5  6  7
 6  7  8  9 10 11 12│  4  5  6  7  8  9 10│  8  9 10 11 12 13 14
13 14 15 16 17 18 19│ 11 12 13 14 15 16 17│ 15 16 17 18 19 20 21
20 21 22 23 24 25 26│ 18 19 20 21 22 23 24│ 22 23 24 25 26 27 28
27 28 29 30         │ 25 26 27 28 29 30 31│ 29 30               
                    │                     │                     

─────────────────────┼─────────────────────┼─────────────────────

        Jul         │         Aug         │         Sep         
Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa
       1  2  3  4  5│                 1  2│     1  2  3  4  5  6
 6  7  8  9 10 11 12│  3  4  5  6  7  8  9│  7  8  9 10 11 12 13
13 14 15 16 17 18 19│ 10 11 12 13 14 15 16│ 14 15 16 17 18 19 20
20 21 22 23 24 25 26│ 17 18 19 20 21 22 23│ 21 22 23 24 25 26 27
27 28 29 30 31      │ 24 25 26 27 28 29 30│ 28 29 30            
                    │ 31                  │                     

─────────────────────┼─────────────────────┼─────────────────────

        Oct         │         Nov         │         Dec         
Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa
          1  2  3  4│                    1│     1  2  3  4  5  6
 5  6  7  8  9 10 11│  2  3  4  5  6  7  8│  7  8  9 10 11 12 13
12 13 14 15 16 17 18│  9 10 11 12 13 14 15│ 14 15 16 17 18 19 20
19 20 21 22 23 24 25│ 16 17 18 19 20 21 22│ 21 22 23 24 25 26 27
26 27 28 29 30 31   │ 23 24 25 26 27 28 29│ 28 29 30 31         
                    │ 30                  │                     </lang>

Perl

This will call to the external program, cal.

<lang perl>$_=$ARGV[0]//1969;`cal $_ >&2`</lang>

PicoLisp

This "calendar" is nicely formatted, and fits into 20 columns ;-) <lang PicoLisp>(de cal (Year)

  (prinl "====== " Year " ======")
  (for Dat (range (date Year 1 1) (date Year 12 31))
     (let D (date Dat)
        (tab (3 3 4 8)
           (when (= 1 (caddr D))
              (get *Mon (cadr D)) )
           (caddr D)
           (day Dat *Day)
           (when (=0 (% (inc Dat) 7))
              (pack "Week " (week Dat)) ) ) ) ) )

(cal 1969)</lang> Output:

====== 1969 ======
Jan  1 Wed        
     2 Thu        
     3 Fri        
     4 Sat        
     5 Sun        
     6 Mon  Week 2
     7 Tue        
....
    28 Sat        
    29 Sun        
    30 Mon Week 27
Jul  1 Tue        
     2 Wed        
     3 Thu        
     4 Fri        
....
    25 Thu        
    26 Fri        
    27 Sat        
    28 Sun        
    29 Mon Week 53
    30 Tue        
    31 Wed

Pike

the Calendar in Pike does not handle the transitions from the Julian to the Gregorian calendar, but it handles those separately. the default calendar is ISO, other options are Gregorian, Julian, Bahai, Coptic, Islamic and Discordian.

this script also highlights holidays by region. regions may be chosen by 2-letter country name, as well as some special 'regions': christianity, orthodox, bahai, islamic, among others.

<lang Pike>

  1. !/bin/env pike

int main(int argc, array(string) argv) {

   object cal = Calendar;
   object year;
   string region = "us";
   array date = argv[1..];
   if (sizeof(date) && objectp(Calendar[date[0]]) && Calendar[date[0]]->Day)
   {
       cal = Calendar[date[0]];
       date = Array.shift(date)[1];
   }
   if (sizeof(date) && (int)date[0])
   {
       year = cal.Year((int)date[0]);
       date = Array.shift(date)[1];
   }
   if (sizeof(date))
       region = date[0];
   if (!year)
       year = cal.Year();
   print_year(year, region);

}

array make_month(object month, int field_width, void|string region) {

   array out =({});
   mapping holidays = ([]);
   object today = Calendar.Day();
   if (region)
       holidays = Calendar.Events.find_region(region)->scan_events(month);
   array weekday_names = sprintf("%*.*s", field_width, field_width, month->week()->days()->week_day_shortname()[*]);
   out += ({ ({ month->month_name(), month->month_no(), month->year_name() }) });
   out += ({ weekday_names });
   out += showday(month->weeks()->days()[*][*], month, today, holidays, field_width);  
   out += ({ ({ " "*field_width })*sizeof(weekday_names) });
   return out;

}

string print_month(object _month, void|int field_width, void|string region) {

   if (!field_width)
       field_width = 2;
   array month = make_month(_month, field_width, region);
   string out = "";
   out += sprintf("%|*s\n", (field_width+1)*sizeof(month[1])-1, sprintf("%s", month[0][0])); 
   out += sprintf((month[1..][*]*" ")*"\n");
   return out;

}

string print_year(object year, void|string region) {

       array output = ({});
       int day_width = 2;
       int columns = Stdio.stdout.tcgetattr()->columns;
       int month_width = sizeof(make_month(year->month(), day_width)[1]) * (day_width+1) - 1;
       if (columns < month_width)
           columns = month_width;
       // try to find an optimal good looking solution to spread the months
       // across the terminal width
       // for the common calendar of 12 months this is easy but we need to
       // account for caledars that have more than 12 months
       float max_width = (float)((columns+2)/(month_width+2));
       float max_height = ceil(year->number_of_months()/max_width);
       float w = max_width;
       
       while(ceil(year->number_of_months()/(w-1)) == max_height)
           w--;
       
       foreach(print_month(year->months()[*], day_width, region)/w;; array row)
       {
           array rows = row[*]/"\n";
           int l = max(@sizeof(rows[*]));
           foreach(rows; int i;)
           {
               // the last line of each month is an empty line.
               // repeat the line as many times as needed to make the months equally long
               rows[i]+=({ rows[i][-1] })*(l-sizeof(rows[i]));
           }
           rows = Array.transpose(rows);
           output += rows[*]*"  ";
       }
       write("%*|s\n", sizeof(output[1]), year->format_nice());
       write(output * "\n");
       write("\n");

}

string showday(object day, object month, object today, mapping holidays, int field_width) {

   string dayname;
   if (day->month() == month)
   {
       dayname = (string)day->month_day();
       dayname = " "*(sizeof((string)month->number_of_days())-sizeof(dayname))+dayname;
       if (day == today)
           dayname = sprintf("%|*.*s", field_width, field_width, dayname);
       else
           dayname = sprintf("%|*.*s", field_width, field_width, dayname);
       if (holidays[day])
           dayname = sprintf("%|s", dayname);
   }
   else
       dayname = " "*field_width;
   return dayname;

} </lang> Output: (holidays lost in copy-paste)

                              1969                              
      January               February               March        
Mo Tu We Th Fr Sa Su  Mo Tu We Th Fr Sa Su  Mo Tu We Th Fr Sa Su
       1  2  3  4  5                  1  2                  1  2
 6  7  8  9 10 11 12   3  4  5  6  7  8  9   3  4  5  6  7  8  9
13 14 15 16 17 18 19  10 11 12 13 14 15 16  10 11 12 13 14 15 16
20 21 22 23 24 25 26  17 18 19 20 21 22 23  17 18 19 20 21 22 23
27 28 29 30 31        24 25 26 27 28        24 25 26 27 28 29 30
                                            31                  
                                                                
       April                  May                   June        
Mo Tu We Th Fr Sa Su  Mo Tu We Th Fr Sa Su  Mo Tu We Th Fr Sa Su
    1  2  3  4  5  6            1  2  3  4                     1
 7  8  9 10 11 12 13   5  6  7  8  9 10 11   2  3  4  5  6  7  8
14 15 16 17 18 19 20  12 13 14 15 16 17 18   9 10 11 12 13 14 15
21 22 23 24 25 26 27  19 20 21 22 23 24 25  16 17 18 19 20 21 22
28 29 30              26 27 28 29 30 31     23 24 25 26 27 28 29
                                            30                  
                                                                
        July                 August              September      
Mo Tu We Th Fr Sa Su  Mo Tu We Th Fr Sa Su  Mo Tu We Th Fr Sa Su
    1  2  3  4  5  6               1  2  3   1  2  3  4  5  6  7
 7  8  9 10 11 12 13   4  5  6  7  8  9 10   8  9 10 11 12 13 14
14 15 16 17 18 19 20  11 12 13 14 15 16 17  15 16 17 18 19 20 21
21 22 23 24 25 26 27  18 19 20 21 22 23 24  22 23 24 25 26 27 28
28 29 30 31           25 26 27 28 29 30 31  29 30               
                                                                
      October               November              December      
Mo Tu We Th Fr Sa Su  Mo Tu We Th Fr Sa Su  Mo Tu We Th Fr Sa Su
       1  2  3  4  5                  1  2   1  2  3  4  5  6  7
 6  7  8  9 10 11 12   3  4  5  6  7  8  9   8  9 10 11 12 13 14
13 14 15 16 17 18 19  10 11 12 13 14 15 16  15 16 17 18 19 20 21
20 21 22 23 24 25 26  17 18 19 20 21 22 23  22 23 24 25 26 27 28
27 28 29 30 31        24 25 26 27 28 29 30  29 30 31            
                                                        

Python

The Python calendar.pryear function prints calendars with the following formatting options: optional parameters w, l, and c are for date column width, lines per week, and number of spaces between month columns, respectively.

Although rumoured to be getting an anti-gravity module, Python as yet does not include a snoopy module ;-) <lang python>>>> import calendar >>> help(calendar.prcal) Help on method pryear in module calendar:

pryear(self, theyear, w=0, l=0, c=6, m=3) method of calendar.TextCalendar instance

   Print a years calendar.

>>> calendar.prcal(1969)

                                 1969
     January                   February                   March

Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su

      1  2  3  4  5                      1  2                      1  2
6  7  8  9 10 11 12       3  4  5  6  7  8  9       3  4  5  6  7  8  9

13 14 15 16 17 18 19 10 11 12 13 14 15 16 10 11 12 13 14 15 16 20 21 22 23 24 25 26 17 18 19 20 21 22 23 17 18 19 20 21 22 23 27 28 29 30 31 24 25 26 27 28 24 25 26 27 28 29 30

                                                   31
      April                      May                       June

Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su

   1  2  3  4  5  6                1  2  3  4                         1
7  8  9 10 11 12 13       5  6  7  8  9 10 11       2  3  4  5  6  7  8

14 15 16 17 18 19 20 12 13 14 15 16 17 18 9 10 11 12 13 14 15 21 22 23 24 25 26 27 19 20 21 22 23 24 25 16 17 18 19 20 21 22 28 29 30 26 27 28 29 30 31 23 24 25 26 27 28 29

                                                   30
       July                     August                  September

Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su

   1  2  3  4  5  6                   1  2  3       1  2  3  4  5  6  7
7  8  9 10 11 12 13       4  5  6  7  8  9 10       8  9 10 11 12 13 14

14 15 16 17 18 19 20 11 12 13 14 15 16 17 15 16 17 18 19 20 21 21 22 23 24 25 26 27 18 19 20 21 22 23 24 22 23 24 25 26 27 28 28 29 30 31 25 26 27 28 29 30 31 29 30

     October                   November                  December

Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su

      1  2  3  4  5                      1  2       1  2  3  4  5  6  7
6  7  8  9 10 11 12       3  4  5  6  7  8  9       8  9 10 11 12 13 14

13 14 15 16 17 18 19 10 11 12 13 14 15 16 15 16 17 18 19 20 21 20 21 22 23 24 25 26 17 18 19 20 21 22 23 22 23 24 25 26 27 28 27 28 29 30 31 24 25 26 27 28 29 30 29 30 31

>>> print('1234567890'*8) 12345678901234567890123456789012345678901234567890123456789012345678901234567890 >>> </lang>

Ruby

Date class, from the standard library, knows how many days in a month, and which day is Sunday, for both Julian and Gregorian calendars. This program uses Date class, plus its own assumptions, to create the calendar. This program assumes that every year has 12 months and starts with January 1, and every month fits in 6 weeks starting with Sunday.

  • This program requires Ruby 1.8.7 because it calls Array#each_slice.
Works with: Ruby version 1.8.7

<lang ruby>require 'date'

  1. Creates a calendar of _year_. Returns this calendar as a multi-line
  2. string fit to _columns_.

def cal(year, columns)

 # Start at January 1.
 #
 # Date::ENGLAND marks the switch from Julian calendar to Gregorian
 # calendar at 1752 September 14. This removes September 3 to 13 from
 # year 1752. (By fortune, it keeps January 1.)
 #
 date = Date.new(year, 1, 1, Date::ENGLAND)
 # Collect calendars of all 12 months.
 months = (1..12).collect do |month|
   rows = [Date::MONTHNAMES[month].center(20), "Su Mo Tu We Th Fr Sa"]
   # Make array of 42 days, starting with Sunday.
   days = []
   date.wday.times { days.push "  " }
   while date.month == month
     days.push("%2d" % date.mday)
     date += 1
   end
   (42 - days.length).times { days.push "  " }
   days.each_slice(7) { |week| rows.push(week.join " ") }
   next rows
 end
 # Calculate months per row (mpr).
 #  1. Divide columns by 22 columns per month, rounded down. (Pretend
 #     to have 2 extra columns; last month uses only 20 columns.)
 #  2. Decrease mpr if 12 months would fit in the same months per
 #     column (mpc). For example, if we can fit 5 mpr and 3 mpc, then
 #     we use 4 mpr and 3 mpc.
 mpr = (columns + 2).div 22
 mpr = 12.div((12 + mpr - 1).div mpr)
 # Use 20 columns per month + 2 spaces between months.
 width = mpr * 22 - 2
 # Join months into calendar.
 rows = ["[Snoopy]".center(width), "#{year}".center(width)]
 months.each_slice(mpr) do |slice|
   slice[0].each_index do |i|
     rows.push(slice.map {|a| a[i]}.join "  ")
   end
 end
 return rows.join("\n")

end


ARGV.length == 1 or abort "usage: #{$0} year"

  1. Guess width of terminal.
  2. 1. Obey environment variable COLUMNS.
  3. 2. Try to require 'io/console' from Ruby 1.9.3.
  4. 3. Try to run `tput co`.
  5. 4. Assume 80 columns.

columns = begin Integer(ENV["COLUMNS"] || "")

         rescue
           begin require 'io/console'; IO.console.winsize[1]
           rescue LoadError
             begin Integer(`tput co`)
             rescue
               80; end; end; end

puts cal(Integer(ARGV[0]), columns)</lang>

Here is 1969 in 132 columns.

$ ruby cal.rb 1969                                                             
                                                             [Snoopy]                                                             
                                                               1969                                                               
      January               February               March                 April                  May                   June        
Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa
          1  2  3  4                     1                     1         1  2  3  4  5               1  2  3   1  2  3  4  5  6  7
 5  6  7  8  9 10 11   2  3  4  5  6  7  8   2  3  4  5  6  7  8   6  7  8  9 10 11 12   4  5  6  7  8  9 10   8  9 10 11 12 13 14
12 13 14 15 16 17 18   9 10 11 12 13 14 15   9 10 11 12 13 14 15  13 14 15 16 17 18 19  11 12 13 14 15 16 17  15 16 17 18 19 20 21
19 20 21 22 23 24 25  16 17 18 19 20 21 22  16 17 18 19 20 21 22  20 21 22 23 24 25 26  18 19 20 21 22 23 24  22 23 24 25 26 27 28
26 27 28 29 30 31     23 24 25 26 27 28     23 24 25 26 27 28 29  27 28 29 30           25 26 27 28 29 30 31  29 30               
                                            30 31                                                                                 
        July                 August              September              October               November              December      
Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa
       1  2  3  4  5                  1  2      1  2  3  4  5  6            1  2  3  4                     1      1  2  3  4  5  6
 6  7  8  9 10 11 12   3  4  5  6  7  8  9   7  8  9 10 11 12 13   5  6  7  8  9 10 11   2  3  4  5  6  7  8   7  8  9 10 11 12 13
13 14 15 16 17 18 19  10 11 12 13 14 15 16  14 15 16 17 18 19 20  12 13 14 15 16 17 18   9 10 11 12 13 14 15  14 15 16 17 18 19 20
20 21 22 23 24 25 26  17 18 19 20 21 22 23  21 22 23 24 25 26 27  19 20 21 22 23 24 25  16 17 18 19 20 21 22  21 22 23 24 25 26 27
27 28 29 30 31        24 25 26 27 28 29 30  28 29 30              26 27 28 29 30 31     23 24 25 26 27 28 29  28 29 30 31         
                      31                                                                30                                        

The output in 80 columns is similar, except that there are only three months per row, and the "[Snoopy]" and "1969" are centered above February.

Seed7

<lang seed7>$ include "seed7_05.s7i";

 include "time.s7i";

const func string: center (in string: stri, in integer: length) is

 return ("" lpad (length - length(stri)) div 2 <& stri) rpad length;

const proc: printCalendar (in integer: year, in integer: cols) is func

 local
   var time: date is time.value;
   var integer: dayOfWeek is 0;
   const array string: monthNames is [] ("January", "February", "March", "April", "May", "June",
       "July", "August", "September", "October", "November", "December"); 
   var array array string: monthTable is 12 times 9 times "";
   var string: str is "";
   var integer: month is 0;
   var integer: position is 0;
   var integer: row is 0;
   var integer: column is 0;
   var integer: line is 0;
 begin
   for month range 1 to 12 do
     monthTable[month][1] := " " & center(monthNames[month], 20);
     monthTable[month][2] := " Mo Tu We Th Fr Sa Su";
     date := date(year, month, 1);
     dayOfWeek := dayOfWeek(date);
     for position range 1 to 43 do
       if position >= dayOfWeek and position - dayOfWeek < daysInMonth(date.year, date.month) then
         str := succ(position - dayOfWeek) lpad 3;
       else
         str := "" lpad 3;
       end if;
       monthTable[month][3 + pred(position) div 7] &:= str;
     end for;
   end for;
   writeln(center("[Snoopy Picture]", cols * 24 + 4));
   writeln(center(str(year),cols * 24 + 4));
   writeln;
   for row range 1 to succ(11 div cols) do
     for line range 1 to 9 do
       for column range 1 to cols do
         if pred(row) * cols + column <= 12 then
           write("   " & monthTable[pred(row) * cols + column][line]);
         end if;
       end for;
       writeln;
     end for;
   end for;
 end func;

const proc: main is func

 begin
   printCalendar(1969, 3);
 end func;</lang>

Original source: [1]

The output of this program is:

                              [Snoopy Picture]                              
                                    1969                                    

          January                 February                 March        
    Mo Tu We Th Fr Sa Su    Mo Tu We Th Fr Sa Su    Mo Tu We Th Fr Sa Su
           1  2  3  4  5                    1  2                    1  2
     6  7  8  9 10 11 12     3  4  5  6  7  8  9     3  4  5  6  7  8  9
    13 14 15 16 17 18 19    10 11 12 13 14 15 16    10 11 12 13 14 15 16
    20 21 22 23 24 25 26    17 18 19 20 21 22 23    17 18 19 20 21 22 23
    27 28 29 30 31          24 25 26 27 28          24 25 26 27 28 29 30
                                                    31                  
                  
           April                    May                     June        
    Mo Tu We Th Fr Sa Su    Mo Tu We Th Fr Sa Su    Mo Tu We Th Fr Sa Su
        1  2  3  4  5  6              1  2  3  4                       1
     7  8  9 10 11 12 13     5  6  7  8  9 10 11     2  3  4  5  6  7  8
    14 15 16 17 18 19 20    12 13 14 15 16 17 18     9 10 11 12 13 14 15
    21 22 23 24 25 26 27    19 20 21 22 23 24 25    16 17 18 19 20 21 22
    28 29 30                26 27 28 29 30 31       23 24 25 26 27 28 29
                                                    30                  
                  
            July                   August                September      
    Mo Tu We Th Fr Sa Su    Mo Tu We Th Fr Sa Su    Mo Tu We Th Fr Sa Su
        1  2  3  4  5  6                 1  2  3     1  2  3  4  5  6  7
     7  8  9 10 11 12 13     4  5  6  7  8  9 10     8  9 10 11 12 13 14
    14 15 16 17 18 19 20    11 12 13 14 15 16 17    15 16 17 18 19 20 21
    21 22 23 24 25 26 27    18 19 20 21 22 23 24    22 23 24 25 26 27 28
    28 29 30 31             25 26 27 28 29 30 31    29 30               
                                                                        
                  
          October                 November                December      
    Mo Tu We Th Fr Sa Su    Mo Tu We Th Fr Sa Su    Mo Tu We Th Fr Sa Su
           1  2  3  4  5                    1  2     1  2  3  4  5  6  7
     6  7  8  9 10 11 12     3  4  5  6  7  8  9     8  9 10 11 12 13 14
    13 14 15 16 17 18 19    10 11 12 13 14 15 16    15 16 17 18 19 20 21
    20 21 22 23 24 25 26    17 18 19 20 21 22 23    22 23 24 25 26 27 28
    27 28 29 30 31          24 25 26 27 28 29 30    29 30 31            
                                                                        
                  

Tcl

Due to the prevalence of 80 column devices instead of 132 column ones, this code produces 3 months at a time instead of 4. <lang tcl>package require Tcl 8.5

  1. Produce information about the days in a month, without any assumptions about
  2. what those days actually are.

proc calMonthDays {timezone locale year month} {

   set days {}
   set moment [clock scan [format "%04d-%02d-00 12:00" $year $month] \

-timezone $timezone -locale $locale -format "%Y-%m-%d %H:%M"]

   while 1 {

set moment [clock add $moment 1 day] lassign [clock format $moment -timezone $timezone -locale $locale \ -format "%m %d %u"] m d dow if {[scan $m %d] != $month} { return $days } lappend days $moment [scan $d %d] $dow

   }

}

proc calMonth {year month timezone locale} {

   set dow 0
   set line ""
   set lines {}
   foreach {t day dayofweek} [calMonthDays $timezone $locale $year $month] {

if {![llength $lines]} {lappend lines $t} if {$dow > $dayofweek} { lappend lines [string trimright $line] set line "" set dow 0 } while {$dow < $dayofweek-1} { append line " " incr dow } append line [format "%2d " $day] set dow $dayofweek

   }
   lappend lines [string trimright $line]

}

proc cal3Month {year month timezone locale} {

   # Extract the month data
   set d1 [lassign [calMonth $year $month $timezone $locale] t1]; incr month
   set d2 [lassign [calMonth $year $month $timezone $locale] t2]; incr month
   set d3 [lassign [calMonth $year $month $timezone $locale] t3]
   # Print the header line of month names
   foreach t [list $t1 $t2 $t3] {

set m [clock format $t -timezone $timezone -locale $locale -format "%B"] set l [expr {10 + [string length $m]/2}] puts -nonewline [format "%-25s" [format "%*s" $l $m]]

   }
   puts ""
   # Print the month days
   foreach l1 $d1 l2 $d2 l3 $d3 {

puts [format "%-25s%-25s%s" $l1 $l2 $l3]

   }

}

proc cal {{year ""} {timezone :localtime} {locale en}} {

   if {$year eq ""} {

set year [clock format [clock seconds] -format %Y]

   }
   puts [format "%40s" "-- $year --"]
   foreach m {1 4 7 10} {

puts "" cal3Month $year $m $timezone $locale

   }

}

proc snoopy {} {

   puts [format "%43s\n" {[Snoopy Picture]}]

}

snoopy cal</lang> Which produces this output:

                           [Snoopy Picture]

                              -- 2011 --

      January                  February                  March             
                1  2         1  2  3  4  5  6         1  2  3  4  5  6
 3  4  5  6  7  8  9      7  8  9 10 11 12 13      7  8  9 10 11 12 13
10 11 12 13 14 15 16     14 15 16 17 18 19 20     14 15 16 17 18 19 20
17 18 19 20 21 22 23     21 22 23 24 25 26 27     21 22 23 24 25 26 27
24 25 26 27 28 29 30     28                       28 29 30 31
31                                                

       April                     May                      June             
             1  2  3                        1            1  2  3  4  5
 4  5  6  7  8  9 10      2  3  4  5  6  7  8      6  7  8  9 10 11 12
11 12 13 14 15 16 17      9 10 11 12 13 14 15     13 14 15 16 17 18 19
18 19 20 21 22 23 24     16 17 18 19 20 21 22     20 21 22 23 24 25 26
25 26 27 28 29 30        23 24 25 26 27 28 29     27 28 29 30
                         30 31                    

        July                    August                 September           
             1  2  3      1  2  3  4  5  6  7               1  2  3  4
 4  5  6  7  8  9 10      8  9 10 11 12 13 14      5  6  7  8  9 10 11
11 12 13 14 15 16 17     15 16 17 18 19 20 21     12 13 14 15 16 17 18
18 19 20 21 22 23 24     22 23 24 25 26 27 28     19 20 21 22 23 24 25
25 26 27 28 29 30 31     29 30 31                 26 27 28 29 30

      October                  November                 December           
                1  2         1  2  3  4  5  6               1  2  3  4
 3  4  5  6  7  8  9      7  8  9 10 11 12 13      5  6  7  8  9 10 11
10 11 12 13 14 15 16     14 15 16 17 18 19 20     12 13 14 15 16 17 18
17 18 19 20 21 22 23     21 22 23 24 25 26 27     19 20 21 22 23 24 25
24 25 26 27 28 29 30     28 29 30                 26 27 28 29 30 31
31                                                

If a different year is chosen, it's printed… <lang tcl>snoopy cal 1969</lang>

                           [Snoopy Picture]

                              -- 1969 --

      January                  February                  March             
       1  2  3  4  5                     1  2                     1  2
 6  7  8  9 10 11 12      3  4  5  6  7  8  9      3  4  5  6  7  8  9
13 14 15 16 17 18 19     10 11 12 13 14 15 16     10 11 12 13 14 15 16
20 21 22 23 24 25 26     17 18 19 20 21 22 23     17 18 19 20 21 22 23
27 28 29 30 31           24 25 26 27 28           24 25 26 27 28 29 30
                                                  31

       April                     May                      June             
    1  2  3  4  5  6               1  2  3  4                        1
 7  8  9 10 11 12 13      5  6  7  8  9 10 11      2  3  4  5  6  7  8
14 15 16 17 18 19 20     12 13 14 15 16 17 18      9 10 11 12 13 14 15
21 22 23 24 25 26 27     19 20 21 22 23 24 25     16 17 18 19 20 21 22
28 29 30                 26 27 28 29 30 31        23 24 25 26 27 28 29
                                                  30

        July                    August                 September           
    1  2  3  4  5  6                  1  2  3      1  2  3  4  5  6  7
 7  8  9 10 11 12 13      4  5  6  7  8  9 10      8  9 10 11 12 13 14
14 15 16 17 18 19 20     11 12 13 14 15 16 17     15 16 17 18 19 20 21
21 22 23 24 25 26 27     18 19 20 21 22 23 24     22 23 24 25 26 27 28
28 29 30 31              25 26 27 28 29 30 31     29 30

      October                  November                 December           
       1  2  3  4  5                     1  2      1  2  3  4  5  6  7
 6  7  8  9 10 11 12      3  4  5  6  7  8  9      8  9 10 11 12 13 14
13 14 15 16 17 18 19     10 11 12 13 14 15 16     15 16 17 18 19 20 21
20 21 22 23 24 25 26     17 18 19 20 21 22 23     22 23 24 25 26 27 28
27 28 29 30 31           24 25 26 27 28 29 30     29 30 31

The code also handles Julian/Gregorian switch dates correctly, but must be told what locale to format the switch as and for what timezone in that case. For example, Spain was one of the first countries to make the change: <lang tcl>snoopy cal 1582 :Europe/Madrid es_ES</lang>

                           [Snoopy Picture]

                              -- 1582 --

       enero                   febrero                   marzo             
 1  2  3  4  5  6  7               1  2  3  4               1  2  3  4
 8  9 10 11 12 13 14      5  6  7  8  9 10 11      5  6  7  8  9 10 11
15 16 17 18 19 20 21     12 13 14 15 16 17 18     12 13 14 15 16 17 18
22 23 24 25 26 27 28     19 20 21 22 23 24 25     19 20 21 22 23 24 25
29 30 31                 26 27 28                 26 27 28 29 30 31

       abril                     mayo                    junio             
                   1         1  2  3  4  5  6                  1  2  3
 2  3  4  5  6  7  8      7  8  9 10 11 12 13      4  5  6  7  8  9 10
 9 10 11 12 13 14 15     14 15 16 17 18 19 20     11 12 13 14 15 16 17
16 17 18 19 20 21 22     21 22 23 24 25 26 27     18 19 20 21 22 23 24
23 24 25 26 27 28 29     28 29 30 31              25 26 27 28 29 30
30                                                

       julio                    agosto                 septiembre          
                   1            1  2  3  4  5                     1  2
 2  3  4  5  6  7  8      6  7  8  9 10 11 12      3  4  5  6  7  8  9
 9 10 11 12 13 14 15     13 14 15 16 17 18 19     10 11 12 13 14 15 16
16 17 18 19 20 21 22     20 21 22 23 24 25 26     17 18 19 20 21 22 23
23 24 25 26 27 28 29     27 28 29 30 31           24 25 26 27 28 29 30
30 31                                             

      octubre                 noviembre                diciembre           
 1  2  3  4 15 16 17      1  2  3  4  5  6  7            1  2  3  4  5
18 19 20 21 22 23 24      8  9 10 11 12 13 14      6  7  8  9 10 11 12
25 26 27 28 29 30 31     15 16 17 18 19 20 21     13 14 15 16 17 18 19
                         22 23 24 25 26 27 28     20 21 22 23 24 25 26
                         29 30                    27 28 29 30 31

As can be seen, a Real Programmer has many intricacies to deal with!