cal

Display a calendar.

Syntax
      cal [-smjy13] [[[day] month] year] 

      ncal [-smjy13] [[[day] month] year]

Key:
   -1    Display single month output. (default)

   -3    Display prev/current/next month output.

   -s    Display Sunday as the first day of the week.

   -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.

   -V    Display version information and exit.

If a single parameter is provided, that will specify a 4 digit year (1 - 9999) to display.

If two parameters are provided, they will denote the Month (1 - 12) and Year (1 - 9999).

If no arguments are specified, the current month is displayed.

cal Displays weeks starting on Sunday, even though most locales start the week on Monday.

ncal (New Calendar) Displays a vertical layout starting on Monday and displays the date of easter.
The ncal format makes a year fit on a 25x80 terminal.

If no parameters are specified, the current month’s calendar is displayed.

The year must be specified with 4 digits. A year starts on 01 Jan.

Examples

Show the calendar for 2027:

$ cal 2027

Show a calendar for the current year with weeks starting on Monday:

$ ncal -m

“If everything seems under control, then you're not going fast enough” ~ Mario Andretti

Related linux commands

dc - Desk Calculator.
factor - Print prime factors.
units - Convert units from one scale to another.
wc - Print byte, word, and line counts.
Calculate the day of the week, for any date, in your head.
Equivalent Windows command: SET /A command does basic arithmetic.