cal command is a calendar command in Linux which is used to see the calendar of a specific month or a whole year.

Syntax:

cal [ [ month ] year]

Rectangular bracket means it is optional, so if used without option, it will display a calendar of current month and year.

$ cal
   February 2020
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