Year 1900 (MCM) was an exceptional common year starting on Monay (link will display the full calendar) of the Gregorian calendar, but a leap year starting on Saturday of the Julian calendar. As a result, the Julian calendar was 12 days behind the Gregorian calendar until Wednesday, February 28 (O.S. February 16) and has been 13 days behind since Thursday, March 1 (O.S. February 17).