[pmontra]

Time was the same for the people that were measuring it with the same tools.

Western sundials started with 12 hours as they worked only during the day [1] and people that were not measuring time eventually measured it with a 24 hours system.

I could not find many sources about Chinese sundials but from the pictures at [2] you can see that they had 12 hours in all the day. A hour on the second sundial is divided in 8 parts. The one in the first picture seems to have the same 8 characters as the other one but each hour is divided into 2 parts, each divided in 4 parts.

I'm not surprised that everybody settled around some small and convenient number. 12 has more factors than 10 and dividing by 2 is more convenient than dividing by 3. I would be surprised to find a 9 or a 15.

[1] https://en.wikipedia.org/wiki/History_of_sundials

[2] https://sonofchina.com/what-is-a-sundial-and-how-does-it-wor...