The past simple is used for actionA general term expressing that somebody or something does somethings that took place over a complete period of timeA period of time that has finished and does not include the time of speaking. E.g.: Geoffrey didn’t go skiing last year. ("last year") in the past. This period is expressed with a time expressionA word or group of words used in a particular situation. E.g.: Good morning, at six, on the sofa, however, the exact time may or may not be mentioned.

Pterodactyls existed between 1550 million and 70 million yeas ago.
From 1981 to 1984 he worked for Coca-Cola.
Last week I stayed with my sister for a few days. (the exact time is not mentioned)
Joe lived in Boston for ten years. (the exact time is not mentioned)

Diagrams

Past simple for past habits and states
Past simple Past simple to express a point in the past