Year a leap year there are 366 days. A leap year occurs every fourth year, or leap year, during which a leap day is intercalated into the month of February. The name "Leap Day" is applied to the added day. The Revised Julian calendar, proposed in 1923 and used in some Eastern Orthodox Churches, has 218 leap years every 900 years, for the average (mean) year length of days, close to the length of the mean tropical year, days (relative error of 9·10). In the year 2800 CE, the Gregorian and Revised Julian calendars will begin to differ by one calendar
Month quarter of a day shorter than the solar year and stellar events "wandered" through the calendar, it is referred to as Annus Vagus or "Wandering Year". The Nisga'a calendar coincides with the Gregorian calendar with each month referring to the type of harvesting that is done during the month. This calendar was proposed during the French Revolution, and used by the French government for about twelve years from late 1793. There were twelve months of 30 days each, grouped into three ten-day weeks called "décades". The five or six extra days needed to approximate the tropical year were placed after