1. When at a particular place, the sun reaches the maximum height in the sky it is assumed that almost half of the daytime is over and this time is considered 12 noon.
2. The time of a particular place as decided by the overhead position of the sun in the sky is considered as the local time of that place.
3. During the rotation of the earth, when a particular longitude comes exactly in front of the sun, it is considered as noontime (12 noon) on that longitude. This noontime is considered as local time of that longitude. In this way, the local time is decided by the noontime.
