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
Positivist calendar Positivist calendar The positivist calendar was a calendar reform proposal by Auguste Comte in 1849. Revising the earlier work of Marco Mastrofini, or an even earlier proposal by "Hirossa Ap-Iccim" (Hugh Jones), Comte developed a solar calendar with 13 months of 28 days, and an additional festival day commemorating the dead, totalling 365 days. This extra day added to the last month was outside the days of the week cycle, and so the first of a month was always a Monday. On leap years, an additional festival day (also outside the week cycle), to celebrate holy women, would join the