I know even ancient humans had systems to keep track of day and night/seasons but around what year did we start using a 24 hour clock? How long did it take to spread? Before the current system were there competing clock systems in place in different parts of the world?
For example, when was someone able to say “it is currently 9:52”?
More may be written, but you might like to start with the FAQ section "Hours, minutes, and seconds" by /u/jeanlucpeckinpah , /u/Acritas , and /u/kookingpot .
This is not to discourage discussion. Further questions, data, and debate are always welcome.