Eli5: Historically, time during the night was measured by ‘watches’; eg. First watch, Second watch, etc. How did people determine when one watch ended and the next began?

Question

It can’t be influenced by the moon or stars in the sky, because how would they measure the time during a moonless cloudy night?

Edit: How would, say, 3 common travellers camping on the road measure time at night?

In: 38

Answer 1

The most common ancient device was the [water clock](https://en.wikipedia.org/wiki/History_of_timekeeping_devices#Water_clocks), which was basically just a tank of water draining at a known rate. Whoever was keeping time – either the watchmen themselves or some centralized timekeeper – could just reset the clock periodically.

Ancient peoples also had hourglasses, although those were developed later and required more engineering work.