We have 24 hours in a day because the people that came up with the sundial lived around the equator (always half a day off light) and counted in base 12. 12 light hours and 12 dark is our 24 hours. You can count base 12 by using your thumb to count the bones in your finger. 4 fingers with 3 bones each gives you 12.

It's also why we have 60 minutes. They counted with their fingers on one hand to 5, with the other to twelve so you get 60. Why not 144? You make mistakes easily when counting to 12 with both hands.

By now there have been many attempts to launch a different system for time keeping and calenders but it never took hold.