cal [-smjy13] [[[day] month] year]
Cal displays a simple calendar. If arguments are not specified, the cur-
rent month is displayed. The options are as follows:
-1 Display single month output. (This is the 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.
A single parameter specifies the year (1 - 9999) to be displayed; note
the year must be fully specified: “cal 89†will not display a calendar
for 1989. Two parameters denote the month (1 - 12) and year. Three
parameters denote the day (1-31), month and year, and the day will be
highlighted if the calendar is displayed on a terminal. If no parameters
are specified, the current month’s calendar is displayed.
A year starts on Jan 1. The first day of the week is determined by the
locale.
The Gregorian Reformation is assumed to have occurred in 1752 on the 3rd
of September. By this time, most countries had recognized the reforma-
tion (although a few did not recognize it until the early 1900’s.) Ten
days following that date were eliminated by the reformation, so the cal-
endar for that month is a bit unusual.