The wonderful cal command can tell you a lot. Entered without any arguments, it shows you a calendar for the current month that looks like this:
$ cal
April 2022
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
But there are several arguments you can add to the cal command to tell you even more. The Julian date, for example. Try this:
$ cal -j 1 2022
The example above produces a rather normal looking calendar, but the -j argument changes it from showing the day of the month (1-31 for January) to the Julian date, or day of the year, instead.
Of course for January, it’s hard to tell the difference. Try this:
$ cal -j 2 2022
February 2022
Su Mo Tu We Th Fr Sa
32 33 34 35 36
37 38 39 40 41 42 43
44 45 46 47 48 49 50
51 52 53 54 55 56 57
58 59
cal Command Examples
1. To display the calender for 2011:
# cal 2011
2. To display single month output:
# cal -1
3. To display previous/current/next month output:
# cal -3
4. To display Sunday as a first day:
# cal -s
5. To display monday as a first day of the output:
# cal -m
6. To display the Julian dates:
# cal -j
7. To display the calender of current year:
# cal -y
8. To display the version information:
# cal -V
Final Thoughts
The cal command writes a Gregorian calendar to standard output. If you specify a four-digit year operand, a calendar for that year is written. If you specify no operands, a calendar for the current month is written. You can display a calendar for any month of any year by specifying the month, as a digit from 1 to 12, followed by any four-digit year up to 9999.