Found in a shipwreck off Antikythera Island in Greece in 1901, the Antikythera Device was built in the 1st century BC and as such is the world’s first known analog computer.
“The mechanism predicts astronomical position, eclipses and the four-year cycle of the ancient Olympic Games. Hipparchus's theory for the motion of the Moon is also used, which suggests the possibility that he may have designed it or at least worked on it.
On the front face of the mechanism there is a fixed ring dial representing the ecliptic, the twelve zodiac signs marked in 30 degree sectors. Outside of that dial is another ring which is rotatable, marked off with the months and days of the Sothic Egyptian calendar twelve months of 30 days plus five intercalary days.”