An ancient Greek device worked like an astronomy calculator.

The Antikythera mechanism used gears to model astronomical cycles more than two thousand years ago.

The Antikythera mechanism is an ancient Greek hand-powered orrery. It is the oldest known example of an analogue computer. It could be used to predict astronomical positions and eclipses decades in advance. It could also be used to track the four-year cycle of athletic games similar to an olympiad, the cycle of the ancient Olympic Games.