When was the first computer invented?

It was either the 40's or the 60's, I can't remember.

During WW11 - 'Collossus' (on view in High Wycombe, UK) to de-code german submarine messages attacking allied Destroyers.

About 2-3 thousand years ago by the Greeks:

"A dictionary-size assemblage of 37 interlocking dials crafted with the precision and complexity of a 19th-century Swiss clock, the Antikythera mechanism was used for modeling and predicting the movements of the heavenly bodies as well as the dates and locations of upcoming Olympic games."

"The original 81 shards of the Antikythera were recovered from under the sea (near the Greek island of Antikythera) in 1902, rusted and clumped together in a nearly indecipherable mass. Scientists dated it to 150 B.C. Such craftsmanship wouldn’t be seen for another 1,000 years — but its purpose was a mystery for decades."