Question

With reference to the International Date Line, state the following:
a)Its meaning and application
b) The important deviations it makes and reasons for the same.
c) Give an example of how time lost or gained is compute with reference to this line.
ICSE Class 9 Total Geography Ch 2:Geographic Grid- Latitudes and Longitudes

Answer 1

It is an imaginary line on the surface of the Earth that runs from the North Pole to the South Pole by passing through the middle of Pacific Ocean and roughly following the 180 longitude.
It demarcates the change of one calendar day to the next one.
It is not a straight line because it zig-zags whenever there is a land to avoid dividing a single place into 2 time zones.
To the left of the International Date Line or in the Eastern Hemisphere, the date is always one day ahead of the date to the right of the International Date Line in the Western Hemisphere.
If you are traveling east across the IDL then you have to subtract a day or 24 hours.If you are traveling  west across the IDL then you have to add a day or 24 hours to your watch and set accordingly.