When an argument is present, calendar does its job for every user who has a file calendar in his or her login directory and sends them any positive results by mail(1). Normally this is done daily by facilities in the UNIX operating system (see cron(1M)).
If the environment variable DATEMSK is set, calendar will use its value as the full path name of a template file containing format strings. The strings consist of field descriptors and text characters and are used to provide a richer set of allowable date formats in different languages by appropriate settings of the environment variables LC_ALL, LC_TIME, and LANG (see environ(5)). The LC_CTYPE environment variable is also examined for details of the codesets used in the format strings. (See date(1) for the allowable list of field descriptors.)
%B %eth of the year %Y
%B represents the full month name, %e the day of month and %Y the year (4 digits). If DATEMSK is set to this template, the following calendar file would be valid:
March 7th of the year 1989 <Reminder>
Your calendar must be public information for you to get reminder service.
calendar's extended idea of ``tomorrow'' does not account for holidays.