French Republican Calendar; Ancient Roman Calendar. Today, most of the West uses the Gregorian calendar, which has its roots in two earlier calendar systems: the Julian calendar and the Roman ...

The confusion grew: "February 30, 1712, came into existence in Sweden when the Julian calendar was restored and two leap days were added that year." Sweden’s final conversion to the Gregorian ...

The Julian calendar officially began on Jan. 1 in 45 BCE. This method would continue over several centuries, but not without issue. Caesar's math of 365.25 days was close, but it wasn't the exact ...

When the Julian calendar was later refined into the Gregorian calendar in 1582, the tradition of adding a leap day to February persisted. Contributing: Saman Shafiq, USA TODAY.

In honor of Leap Day, this read is for the history nerds. Ever wonder how America caught our calendar up with the rest of the world? In September 1752, we skipped over 11 days.

Known as the revised Julian calendar, it was adopted by several Orthodox churches, including the churches of Greece, Cyprus, and Romania. Those churches now celebrate Christmas on December 25.

In the Julian calendar, the new year began on March 25. So March 24, 1701 would be followed directly by March 25, 1702. The Gregorian calendar, as we know today, begins on January 1.