387 B.C.: Plato founds his Academy, which continues to operate in Athens for nine centuries.
300 B.C.: Euclid writes his Elements [pictured: one of the oldest surviving fragments], systematically presenting theorems of geometry and arithmetic.
100 B.C.: A gear-based device, the Antikythera mechanism, is created to compute calendrical computation. It survives today.
45 B.C.: Julius Caesar institutes the Julian calendar, establishing the lengths of the 12 months.
Content courtesy of Wolfram|Alpha