Perpetual Calendar

Since the return of the Jews from Babylonian exile, the day of the Easter festival (Pesach, Pasha) is calculated on the basis of the first full moon after the beginning of spring (March 21). The Christians adopted this regulation for their Easter festival.

The Julian calendar was adopted at the Council of Nicaea (Decree “computus paschalis”) in 325, and for the Easter date it was for the first time already in 326. Also for Orthodox Christians, the calendar today is still valid but the date must be converted to the “bourgeois” calendar.

The German mathematician Carl Friedrich Gauß (1777-1855) was able to calculate the Easter-date for every year – from 1583 to 8201, that is – after the Gregorian calendar reform in October 1582. However, it is still remains unclear whether for the years 3200 or 3600 the leap-year must be dropped to balance a remaining time.

The Leap Year

We all know that the leap year comes every 4th year. We also know that a leap year means that where will be a February 29th. This creates the unique situation whereby someone born on February 29th will only have a birthday every 4 years. Often these people celebrate their sudo birthday on February 28th for those other 3 years.

As you can see from the leap years listed below there are years in which we do not have a leap year. This is as a result of the Gregorian calendar which has us skip a leap year every 100 years to make up for the fact that 11 minutes had to be shaved off the 365.25 year. Historical calendars are more difficult to analyze as different areas of the world adopted the current calendar format at different times. Most countries today use the Gregorian format as opposed to the Julian format. And while we are taught that the leap year being once every four years means that each year is really .25 days longer; the Gregorian calendar accounts for the fact that a year is 11 minutes less than 365.25 days.

Leap year list from 1900 to 2400:

1904 • 1908 • 1912 • 1916 • 1920 • 1924 • 1928 • 1932 • 1936 • 1940 • 1944 • 1948 • 1952 • 1956 • 1960 • 1964 • 1968 • 1972 • 1976 • 1980 • 1984 • 1988 • 1992 • 1996 • 2000 • 2004 • 2008 • 2012 • 2016 • 2020 • 2024 • 2028 • 2032 • 2036 • 2040 • 2044 • 2048 • 2052 • 2056 • 2060 • 2064 • 2068 • 2072 • 2076 • 2080 • 2084 • 2088 • 2092 • 2096 • 2104 • 2108 • 2112 • 2116 • 2120 • 2124 • 2128 • 2132 • 2136 • 2140 • 2144 • 2148 • 2152 • 2156 • 2160 • 2164 • 2168 • 2172 • 2176 • 2180 • 2184 • 2188 • 2192 • 2196 • 2204 • 2208 • 2212 • 2216 • 2220 • 2224 • 2228 • 2232 • 2236 • 2240 • 2244 • 2248 • 2252 • 2256 • 2260 • 2264 • 2268 • 2272 • 2276 • 2280 • 2284 • 2288 • 2292 • 2296 • 2304 • 2308 • 2312 • 2316 • 2320 • 2324 • 2328 • 2332 • 2336 • 2340 • 2344 • 2348 • 2352 • 2356 • 2360 • 2364 • 2368 • 2372 • 2376 • 2380 • 2384 • 2388 • 2392 • 2396 • 2400

How to know if it is a leap year:

leap years are any year that can be evenly divided by 4 (such as 2012, 2016, etc)
except if it can be evenly divided by 100, then it isn’t (such as 2100, 2200, etc)
except if it can be evenly divided by 400, then it is (such as 2000, 2400)

Some Models

Perpetual Calendar by Clayton Boyer

Perpetual Calendar by Bernard Vuarnesson

Perpetual Calendar by Andrei Erdei

Perpetual Calendar by Gideon Dagan

Perpetual Calendar by Steve Ramsey

The Mechanism

Mechanism explained by A. Lange & Söhne

Mechanism explained by SalonQP Magazine

Download

A perpetual calendar (CH) according to C. F. Gauss in Excel format. This downloadable Perpetual Calendar accurately calculates for the period between the years 326 to 3000. For the years before and after: No guarantee. Please enter the desired year in the cell next to where it says “Eingabejahr”. You will also find a sheet with all the Swiss public holidays listed as well as a 10000-year calendar in English.

Perpetual Calendar

If you prefer having generated an online future calendar, you may turn to timeanddate.com

The Limits

A perpetual calender works in the same way as any calendar… it just does so for a loooooooooong period of time. Perpetual after all is a conceptual theory. No one has ever been able to actually put a measure to the concept of perpetual. Seeing that, to measure perpetual, it would have to end at some point and therefore was no longer perpetual. Hence totally killing the idea of perpetual.