Claus har samlet en del oplysninger om kalendere, herunder en samling af ofte stillede spørgsmål om kalendere.

Desværre findes disse sider kun på engelsk, men Claus har også skrevet en bog om kalenderhistorie på dansk.



Calendar FAQ

The Frequently Asked Questions about Calendars document is available here:


The Calendar FAQ includes a number of formulas for calculating various calendar values.

I have written a very simple implementation of these formulas in the C language. Rather than providing the most efficient code, the implementation intentionally follows the formulas very closely.

The code can be downloaded as a ZIP file

The photo below shows a tombstone located in the floor of the North Choir Aisle of Salisbury Cathedral in England. It illustrates how the new year hasn't always started on 1 January.

As described the Calendar FAQ, February had 30 days in Sweden in 1712.

The picture below shows two pages from a Swedish almanac from 1712.

You rarely get to see a 3-digit year in actual use. The photo below shows the date in a document signed by the Holy Roman Emperor Charles III (a.k.a. Charles the Fat) on 2 April 883.

Although a 30 February has indeed occurred in history, what about 31 February?

Translations of older versions of the Calendar FAQ are available in these languages: