Question

The local time is decided by the noon time.(give geographical reason)

Answer 1

hii this is your answer

Time at Greenwich = 7:30 pmGreenwich is the 0°longitude.
Time at given place = 12 pm
Difference between the time at both places = 7 hours 30 mins.
Since the time at given place is less than that at the Greenwich meridian, the place is to the west of it.
It takes 4 minutes for the earth to cover 1°Therefore, it will take 60 minutes (1 hour) to cover 15°So, the Earth will cover 112.5°(15x7.5) in 7.5 hrsThus, the location of the place is 112.5°West

Answer 2

It's a very simple and practical reason.

Since there are three parts/events in a day

Sunrise and sunset are very complex things. For a country/place there are many sunrises for example nautical sunrise, twilight sunrise etc. Also these types have difference of around half or full hour in between. Thus Taking sunrise/sunset would be a very bad idea.

Talking of noon, it is the perfect event to choose local time. It is perfect to a great extent. It's perfection is such that it deviates only around half an hour in a year.