Introduction

Measurement of time by human start in the ancient time, ever since man first noticed the regular movement of the Sun, moon and stars, Time is a moment or duration in which things occur. The understanding of time is essential for our daily life activities. For example, our school starts at a particular ‘time’. We use our wrist watch to know the time so that we may reach the school on time. Similarly, we need to know time to catch a bus, or train for making a journey. We also have to know time to listen to a particular TV. We measure time with the help of clocks and watches.

Natural Events

The earliest natural events to be recognised were in the heavens, but during the course of the year there were many other events that indicated significant changes in the environment. Seasonal winds and rains, the drowning of rivers, the blooming of trees and plants, and the reproduction cycles or migration of animals and birds, all led to natural divisions of the year, and further observation and local customs led to the recognition of the seasons.

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