Or was the concept of an hour much more fluid than now? Were all hourglasses slightly inaccurate and no one was bothered?
From what I could make out of u/kookingpot 's answer here
https://www.reddit.com/r/AskHistorians/comments/3vxb5d/how_were_our_current_units_of_time_agreed_upon/
Time concepts varied until people could make clocks.