Metonic cycle
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The Metonic cycle or enneadecaeteris is a period of almost exactly 19 years after which the lunar phases recur at the same time of the year. The recurrence is not perfect, and by precise observation t
Depiction of the 19 years of the Metonic cycle as a wheel, with the Julian date of the Easter New Moon, from a 9th-century computistic manuscript made in St. Emmeram's Abbey (Clm 14456, fol. 71r)
Antikythera mechanism
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The Antikythera mechanism is an ancient Greek hand-powered orrery built in the 2nd century BC and discovered in 1901. It is the oldest known example of an analogue computer. It could be used to predic
Metonic cycle
…Siculus reports that Apollo is said to have visited the Hyperboreans once every 19 years. The Metonic cycle was implemented in the 2nd century BC Antikythera mechanism, which offers unexpected evidence for the popularity of the calendar based on it. The (19-year) Metonic cycle is a lunisolar cycle, as is the (76-year…
Derek J. de Solla Price (1922–1983) with a model of the Antikythera mechanism
Computer-generated front panel of the Freeth model
Front panel of a 2007 re-creation
Computer-generated back panel