More can be written, but you might start with these two discussions from the FAQ:

"What systems did civilizations use before they were introduced to the hour/minute/second idea? Are any such systems still in use?" by /u/jeanlucpeckinpah

"How were our current units of time agreed upon?" by /u/kookingpot

This is not to discourage discussion. Further questions, data, and debate are welcome. The rules state, "you are still welcome to ask your question if it has been asked before: you may get new answers from different people".