Every task we do takes some Time. Like we do our homework for an hour, we need 15 minutes to reach our school. Usually we will have a routine in our everyday life, where we get up at a specific time, go to school at a specific time and do other such activities throughout the day at specific time. The clock tells us time. Time is calculated in hours, minutes and seconds.
In ancient days, before the clock was invented time was measured by observing the sun and the moon. In the early days some of the devices used to measure time were sun dial, shadow clocks, water clocks, hour glass and others.