Golden number (calendar)
The golden number ( Latin : Numerus aureus ) marks the position of a calendar year of the Christian era within the 19-year lunar circle . The golden numbers 1 to 19 are consecutively assigned to this position, on which the Easter date depends.
Calculation of the golden number
The most commonly given formula for determining the golden number for the year with the year is:
- the calculation type for modulo
- the possible results GZ = 0 , 1,…, 17 or 18.
The result 0 is to be converted to 19 , after which the result series is:
- GZ = 19 , 1, ..., 17 or 18.
The year 2009 has the golden number (2009 + 1) mod 19 = 15.
In 2013, the conversion rule (0 → 19) must be applied:
The year 2013 has the golden number (2013 + 1) mod 19 = 0, i.e. 19.
The following formula leads to the same result (except for the year 1 BC, for which the first formula does not provide a correct result either), without having to apply the conversion rule in exceptional years:
Because of its importance in the calculation of Easter ( Computus (Osterrechnung) ) - the most important festival in Christianity - this auxiliary variable was often written in golden color in late medieval annual calendars, which is said to have resulted in the designation golden number. It is also possible that it got this name because of its outstanding meaning.
|( Year 0 )||( not available in traditional Christian calendar )|
|19 AD||1 (counting starts again from the beginning)|
- When is Easter? (engl.)
- Golden number in a glossary by Hermann Grotefend
- Heinz Zemanek : Calendar and Chronology. Known & unknown from calendar science. An essay. 5th improved edition. Oldenbourg, Munich 1990, ISBN 3-486-20927-2 , pp. 45 and 46.
- Golden number in the glossary www.nabkal (Nikolaus A. Bär) 
- Golden number in the chronology glossary www.phil-gesch.uni-hamburg archive link ( Memento from March 21, 2009 in the Internet Archive )
- Kerstin Springsfeld: Alkuins influence on computistics at the time of Charlemagne. Franz Steiner, Stuttgart 2002, ISBN 3-515-08052-X , p. 37 ( restricted online version (Google Books) ).