Republican calendar

The Republican calendar 🇫🇷 was created during the French Revolution to remove all religious and royalist references from the calendar. This initiative was also part of a larger movement towards decimalisation. It was officially used between 1793 and 1805 in France.

This library allows easy conversion between Gregorian and Republican dates. It can be used for dates after 1805 (see details about non-historical periods below).

Dependency

With Maven, add to your dependencies:

<dependency>
    <groupId>com.github.jarnaud</groupId>
    <artifactId>republican-calendar</artifactId>
    <version>1.3</version>
</dependency>

With SBT:

libraryDependencies += "com.github.jarnaud" % "republican-calendar" % "1.3"

NB: To find the latest version, please refer to Maven search.

Quickstart

Dates

• To convert a Gregorian local date into a Republican date:

LocalDate date = LocalDate.of(1792, 9, 22);
RDate rDate = RDate.of(localDate);

• To convert a Republican date into a Gregorian date:

RDate rDate = RDate.of(1, RMonth.Vendemiaire, 1);
LocalDate date = c.toLocalDate();

• RDate represents a Republican date and provides some utility methods: isBefore(RDate), isSextile(), plusDays(int).

Time

The Republican calendar uses the decimal time. Each day contains 10 hours, each hour contains 100 minutes and each minute contains 100 seconds. You can convert between normal and Republican time to the nanosecond precision that way:

• To convert a normal time into a Republican time:

LocalTime localTime=LocalTime.of(16, 48, 0);
RTime rTime=RTime.of(localTime);

• To convert a Republican time into a normal time:

RTime rTime=RTime.of(7, 0);
LocalTime localTime=rTime.toLocalTime();

Date and time

We provide RDateTime which is an equivalent to LocalDateTime in the Republican calendar. It combines RDate and RTime. You can use it in the same way:

• To convert a normal date and time into a Republican date and time:

LocalDateTime dateTime=LocalDateTime.of(1818,12,12,11,7,58);
RDateTime rdt = RDateTime.of(dateTime);

• To convert a Republican date and time into a normal date and time:

RDateTime rdt = RDateTime.of(27, RMonth.Frimaire, 21, 4, 63, 87);
LocalDateTime dateTime=rdt.toLocalDateTime();

NB: for RTime and RDateTime, it may happen that converting to normal time then back doesn't give the original second. It's because decimal seconds are not aligned with the normal seconds. You can call .roundSecond() on both to round the time to the nearest second.

Non-historical periods

The Republican calendar was used historically between 1791 and 1805. However, we can use this calendar for other dates, based on following rules:

• Dates before 1792-09-22 (first day of Republican calendar) are not defined.
• Dates after 1806-01-01 (end of Republican calendar) are estimated based on the commonly used Romme method.

Links and references

More about the Republican calendar (including current date): https://en.wikipedia.org/wiki/French_Republican_calendar

More about the decimal time: https://en.wikipedia.org/wiki/Decimal_time

Note about online converters: A lot of online converters are incorrect for dates outside the period of real historical usage of the Republican calendar, mostly due to improper handling of leap years.