Display a calendar
SYNTAX
cal [-mjy] [[month] year]
options:
-m Display monday as the first day of the week.
-j Display julian dates (days one-based, numbered from January 1).
-y Display a calendar for the current year.
A single parameter specifies the 4 digit year (1 – 9999) to be displayed.
Two parameters denote the Month (1 – 12) and Year (1 – 9999).
If arguments are not specified, the current month is displayed.
A year starts on 01 Jan.