Cal is a command which displays the calendar for the month and the year.
cal [month] [year]
- Specifies the month for you want the calendar to be displayed. Must be the numeric representation of the month. For example February is 2 and November is 11.
- Specifies the year that you want to display.
displays the calendar for current month.
$ cal 11 2001
displays the calendar for November of 2001.
Most (all?) Linux distributions incorporate this from the [util-linux] project.