Linux / UNIX: displays a calendar and the date of easter with cal command

Q. date command displays date and time under a shell? How do I display calendar under Linux or UNIX?

A. date displays the Linux or UNIX system current date and time. The cal command displays a simple calendar in traditional format and ncal offers an alternative layout, more options and the date of easter. The new format is a little cramped but it makes a year fit on a 25×80 terminal. If arguments are not specified, the current month is displayed.

cal command

Just enter cal command as follows:
$ cal
Output:

    August 2007     
Su Mo Tu We Th Fr Sa
          1  2  3  4
 5  6  7  8  9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31

ncal command

ncal command changes the output format:
$ ncal
Output:

    August 2007
Mo     6 13 20 27   
Tu     7 14 21 28   
We  1  8 15 22 29   
Th  2  9 16 23 30   
Fr  3 10 17 24 31   
Sa  4 11 18 25      
Su  5 12 19 26   

Print calendar for year 2008

$ cal 2008
Output:

                               2008                                

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

Print calendar for particular month and year

Use syntax as follows:
cal {month [1-12]} {year[1-9999]}
For example, display Jan-2007 calendar, enter:
$ cal 1 2007

Print the previous month

To print the previous month, the current month, and the next month all on one row, enter:
$ cal -3

Display Julian Calendar, if combined with the -e option, display date of easter according to the Julian Calendar.

$ cal -J

Display date of easter (for western churches)

$ cal -e

Print a calendar where Monday is the first day of the week, as opposed to Sunday.

$ cal -m

Display Julian days (days one-based, numbered from January 1).

$ cal -j

Display date of orthodox easter (Greek and Russian Orthodox Churches).

$ cal -o
Print the country codes and switching days from Julian to Gregorian Calendar as they are assumed by ncal. The country code as determined from the local environment is marked with an asterisk.
$ cal -p

Print the number of the week below each week column.

cal -w

Display a calendar for the current year.

$ cal -y