Leap year This makes it easy to convert dates to or from Gregorian. The Thai solar calendar uses the Buddhist Era (BE), but has been synchronized with the Gregorian since AD 1941. From AD 8 the Julian calendar received an extra day added to February in years that are multiples of 4. The Coptic calendar and Ethiopian calendar also add an extra day to the end of the year once every four years before a Julian 29-day February. This rule gives an average year length of 365.25 days. However, it is 11 minutes longer than a tropical year. This means that the
Thirty Days Hath September Meton in the 5thcentury. Rather than adopt a new system like the Egyptian calendar, which had 12 months of 30 days each and a set, annual intercalary month of 5 days, Caesar aimed for his 46 reform to maintain as much continuity as possible with the old calendar. Ultimately, Mercedonius was removed, the four existing 31-day months were maintained, February was left unchanged apart from leap years, and the needful additional ten days of the year were added to the 29-day months to make them either 30 or 31 days long. By the Renaissance, the irregularity of the resulting system