French Republican Calendar - Converting From The Gregorian Calendar

Converting From The Gregorian Calendar

The calendar was abolished in the year XIV (1805). After this date, opinions seem to differ on the method by which the leap years would have been determined if the calendar were still in force. There are at least four hypotheses used to convert dates from the Gregorian calendar:

• The leap years would continue to vary in order to ensure that each year the Southward equinox falls on 1 Vendémiaire, as was the case from year I to year XIV. This is the only method that was ever in legal effect, although it means that sometimes five years pass between leap years.
• The leap year would have jumped after year 15 to year 20, after which a leap year would have fallen on each year divisible by four (thus in 20, 24, 28…), except most century years, according to Romme's proposed fixed rules. This would have simplified conversions between the Republican and Gregorian calendars since the Republican leap day would usually follow a few months after 29 February, at the end of each year divisible by four, so that the date of the Republican New Year remains the same (22 September) in the Gregorian calendar for the entire third century of the Republican Era (AD 1992–2091).
• The leap years would have continued in a fixed rule every four years from the last one (thus years 15, 19, 23, 27…) with the leap day added before, rather than after, each year divisible by four, except most century years. This rule has the advantage that it is both simple to calculate and is continuous with every year in which the calendar was in official use during the First Republic. Some concordances were printed in France, after the Republican Calendar was abandoned, using this rule to determine dates for long-term contracts.
• Beginning with year 20, years divisible by four would be leap years, except for years divisible by 128. Remark, that this rule was first proposed by von Mädler, not before the late 19th century. The date of the Republican New Year remains the same (23 September) in the Gregorian calendar every year from 129 to 256 (AD 1920–2047).

The following table shows when several years of the Republican Era begin on the Gregorian calendar, according to each of the four above methods:

* Leap year, extra day added at end of year