Question

The local tike is decided by the noon time

Answer 1

A good question.

Thinking about it, there are three events in a day that are easily observable: sunrise, sunset and noon. In most parts of the world, sunrise and sunset are long-drawn-out things. For example, take Madrid, roughly in the middle of the longitude range for the Western world and look at Sunrise and sunset times in Madrid. Today (22 July) the sunrise has three different times (astronomical twilight, nautical twilight and civil twiight), at 5:07, 5:52 and 6:31. That’s a difference of nearly 1½ hours, and it happens again at sunset (22:10 to 23:33). So sunrise and sunset aren’t useful. That leaves noon, which can be measured relatively accurately.

It’s so accurate, in fact, that people discovered centuries ago that the time of noon deviates by more than half an hour in the course of the year:



So Solar time - Wikipedia (from which I got the graph) time is clearly useless for precise timekeeping, and they introduced the concept of mean solar time, effectively the time along the 0 axis. So midday is only marginally important for our concept of solar time, and time zones muddy that water still more.