21 BC

The year 21 BC (in the proleptic Julian calendar) started on Sunday, January 1, and ended on Monday, December 31. It was (proleptically) a leap year.

Calendar with holidays
Holidays:
 * New Year's Day: Sunday, January 1
 * Leap Day: Wednesday, February 29
 * Halloween: Wednesday, October 31
 * New Year's Eve: Monday, December 31