I mean how did they accurately know at any given point of day what time it was with the nafka mina being shaos zmanios e.g. zman krias shema, plag hamincha etc.
Today, we tend not to take too much notice of astronomical phenomena (unless you have an interest in it). Back in the days before clocks, however, people had a much greater awareness of it. Most people were probably aware of the sun’s path across the sky and could judge just how far along it was at any particular time of the day.
If you know the path the sun is going to take, then it’s no great feat to know when it’s 1/4 of the way there (i.e. 3 hours) or at high noon (chatzos), etc.
Likewise, devices such as sundials could also provide similar information.
The Wolf