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
Mesoamerican calendars ruled the following thirteen days. If the first day of a trecena was auspicious then so were the next twelve days. This 365-day calendar corresponded was divided into 18 'months' of 20 days each, plus 5 'nameless' days at the end of the year. The 365 day year had no leap year so it varied from the solar year by a quarter of a day each year. The years were given their name in much the same way as the days of the 260-day calendar, 20 names were paired with 13 numbers giving 52 different possibilities for year names In