According to Official Guinness Records,
The 2,000-year-old Antikythera Mechanism was discovered in 1900–01 in a shipwreck close to the Greek island of Antikythera. It is a collection of bronze gears encrusted with sea accretions, built with a mechanical complexity that has not been demonstrated in any other object prior to the 14th century. It is regarded as the oldest analog computer and is believed to have been able to predict eclipses.
For a complete list of Unknown date records, please visit Unknown date Guinness Records in Greece.