cal – Displays a calendar
Summary :
Cal displays a simple calendar. If arguments are not specified, the current month is displayed.
Examples :
$ cal — Displays current month
$ cal -3 — Display prev & current & next month output.
$ cal -y — Display a calendar for the current year
$ cal -m — Display Monday as the first day of the week. Sunday is default.
$ cal 2005 — Display a calendar for the year 2005.
$ cal 2 2005 — Display a calendar for the month of Feb 2005.
$ cal 9 1752 — Interesting. http://www.crowl.org/Lawrence/time/britgreg.html
Read : man cal , gcal