CAL is a nicely-enhanced version of the Unix `cal' command.
Features:

 * Hilights today's date when displaying a monthly calendar.
 * Displays an optional user-definable list of `special day'
   descriptions (like appointments) to the right of the monthly
   calendar display.  Cal can be set optionally to ignore appointments
   older than the current day.  Next month's appointments are shown if
   there is room to do so.  Multiple appointment data files may also
   be specified on the commandline.
 * You can specify your own appointment and color definition files on the
   commandline, or use the defaults.
 * Date descriptions can display "years since" a given year, useful for
   birthdays and anniversaries.
 * Completely configurable colors -- eight separate color attributes.
 * No ANSI driver needed for colors, and the output may be redirected
   anywhere, just like the Unix version.  However, ANSI color control may
   be enabled (e.g. for Unix) with a #define in the source code.
 * Commandline-compatible with Unix `cal' command, but with several
   enhanced switch settings.

WWW: http://unicorn.us.com/cal.html