Golden numbers

The golden numbers (sometimes capitalized) are numbers assigned to each year in sequence to indicate the year's position in a 19-year Metonic cycle. They are used in the computus (the calculation of the date of Easter) and also in the Runic calendar. The golden number of any Julian or Gregorian calendar year can be calculated by dividing the year by 19, taking the remainder, and adding 1. (In mathematics this can be expressed as ("year number" modulo "19") +1.) For example, 2008 divided by 19 gives 105, remainder 13. Adding 1 to the remainder gives a golden number of 14.

The term "golden number" was not used in classical times. Its first documented use is in the computistic poem "Massa Compoti" by Alexander de Villa Dei in 1200. Later, a scribe added it to tables originally composed by Abbo of Fleury in 988.