Our ancestors were able to tell the time long before clocks were invented. We figured out that there were certain things that were constant in the world; the sun rising and setting, for example, and started measuring time around that.
In the very early days of humans living on the planet, we would rise with the sun and go to bed with the moon – or, at least, hide from the predators which came out at night.
You could set some particular times – “I’ll meet you by the entrance to the cave when the sun is directly overhead,” or “I want you to be home for lunch when the sun is down as far as that tree in the distance.” That wasn’t very sophisticated, was it?
But then we began to evolve and get cleverer. One of our very first ways of measuring time was with a sun dial, after we figured out the speed of the sun. We built different-sized sundials, some small and some huge, with dials around the outside so that everyone agreed on particular times – “I’ll meet by the sun dial in the town square when the shadow touches VII.”
The ancient Greeks also used water clocks, which obviously didn’t rely on the sun to tell them what the time was. Apparently, these water clocks were mostly used at night, but possibly in the day as well.
Hourglasses were a huge way of measuring a unit of time – they couldn’t tell you what the current time was, but could easily tell you when an hour or a minute has gone past. Nowadays, we use egg timers for pretty much the same thing.
Clocks eventually were created, and there was a lot of confusion for a long time; different towns and villages used their own times, and they didn’t necessarily agree with the time of the next village. Imagine walking 20 minutes to the next town and finding that it was actually two hours ahead!
Countries eventually started to organise things far better and were far more logical; time zones were eventually created, where different countries were grouped together and had their clocks all set to the same time. Everyone knew who was in that time zone, and who was in the next time zone along, so that we could plan ahead. That makes life so much easier, doesn’t it?