Disc perpetual calendar

Reproduction of an 18th century perpetual calendar.

A perpetual calendar is a calendar that is valid for many years. It usually allows you to determine a day or week in the past or future.

This perpetual calendar is valid from 1 January 1600 to 31 December 2799 according to the Sunday letter system.

To determine which day of the week falls on 29 June 1900 (birth of Antoine de St. Exupery), you must first find the Sunday letter for the year 1900.

On the back of the calendar (moon side, second image above), the letter G appears at the intersection of 19 (on the small century disc) and 00 (on the base disc).

The next step is to turn the perpetual calendar.

If you place the month of June (on the movable disc) in front of the Sunday letter G, you can read the day of the week V (Veneris in Latin, Friday in English) in column 29.

The attention to detail, historical interest and beauty of the shapes are what make this perpetual calendar so special. It comes complete with a wooden base and instructions.