Leap year vernal equinox moves a day earlier in the calendar about every 131 years. The Revised Julian calendar adds an extra day to February in years that are multiples of four, except for years that are multiples of 100 that do not leave a remainder of 200 or 600 when divided by 900. This rule agrees with the rule for the Gregorian calendar until 2799. The first year that dates in the Revised Julian calendar will not agree with those in the Gregorian calendar will be 2800, because it will be a leap year in the Gregorian calendar but not in
February 29 − days or 365.2425 days. The length of the tropical year in 2000 was 365.24217 mean solar days, Adding a calendar day every four years, therefore, results in an excess of around 44 minutes every four years, or about 3 days every 400 years. To compensate for this, three days are removed every 400 years. The Gregorian calendar reform implements this adjustment by making an exception to the general rule that there is a leap year every four years. Instead, a year divisible by 100 is not a leap year unless that year is also divisible by 400. This means