When did dinosaurs become extinct?
Dinosaurs went extinct about 65 million years back (at the end of the Cretaceous era), after living on Earth for about 165 million years. If all of Earth time from the extremely beginning of the dinosaurs to today were compressed into 365 days (1 calendar year), the dinosaurs appear January 1 and became extinct the third week of September. (Using this same time scale, the Earth would have formed around 18.5 years earlier.) By comparison, people (Homo sapiens) have been on earth only since December 31 (New Year's eve). The dinosaurs long period of dominance surely makes them unqualified successes in the history of life on Earth.