If a country is large in the east – west expanse, then keeping a single standard time for the entire nation cannot work, because in such countries, the place located in the east and the the place located in extreme west may have a difference of 4 – 5 hours. In countries like Canada and the,United States, this difference is seen in local time in some places.
Marine vessels also experience great difficulty in remembering the local time of each place. To overcome this inconvenience, the whole earth has been divided into 24 parts. All such parts are called time zones. There is only one standard or mean time in each time zone. These time zones are divided into 24 parts so that each time zone has at difference of one hour.
There are 15° longitudes in each time zone. The number of time zones in different countries can vary according to the nation’s expansion. For example: 5 in Canada, 4 in the United States, 3 in Europe, and 11 times zones in Russia. Due to these time zones, there is a similarity of time in these regions, despite their great expanse.
