Tag Archives: date and time

What is the principle behind international date line?

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Suppose you are starting a journey to the east from 180 deg longitude. So every 15 degree of longitude you pass, you have to advance your clocks by one hour. Thus by the time you cover 360 deg and come back to the point you have started, you will find that you have advanced your clocks by 24 hours and hence you have to retard by a day when you cross the 180 deg line again.