Ancient cultures seemed to have no conception of computing beyond arithmetic, algebra, and geometry, occasionally devising computational systems with elements of calculus (e.g. the method of exhaustion). The only mechanical device that existed for numerical computation at the beginning of human history was the abacus, invented in Sumeria circa 2500 BC. Later, the Antikythera mechanism, invented some time around 100 BC in ancient Greece, is the first known mechanical calculator utilizing gears of various sizes and configuration to perform calculations, which tracked the metonic cycle still used in lunar-to-solar calendars, and which is consistent for calculating the dates of the Olympiads.