cal(1) on FreeBSD
The text d5f3c1e4f0cd, as FreeBSD 12.4-RELEASE shipped it.
displays a calendar and the date of Easter
Flags it lists
-
-3 -
-A -
-B -
-C -
-H -
-J -
-N -
-d -
-e -
-h -
-j -
-m -
-o -
-p -
-s -
-w -
-y