about

the metonic cycle is a period of 19 years corresponding to almost exactly 235 synodic months or lunar phases. named after meton of athens, a greek mathematician and astronomer from the 5th century bc, the cycle provides a framework for building lunisolar calendars by synchronizing the solar year with the lunar month.

a mechanical lunisolar calculator based on the metonic cycle is integrated into the antikythera mechanism, a hand-powered model of the solar system built in the 2nd century bc. this virtual model simulates a gearing system inspired by the antikythera mechanism, following the ratio ²³⁵⁄₁₉ = ⁴⁷⁄₁₄ × ⁷⁰⁄₁₉ ≈ 12.37. the second gear ratio is ³⁵⁄₁₉ with a rotating disc covering two moon phases per full turn. the calculator was calibrated as of new moon on november 1 2024 1:47 pm and will deviate by one day in 60.5 years.

controls on the right allow for toggling between animation and the current moon phase as well as jumping to the next or previous new or full moon. the calculated date is indicated at the bottom. the animation speed is set to one solar year per minute.

contact:
prof. thomas weibel
university of applied sciences of the grisons
berne university of the arts
switzerland

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