If each town were to keep the time of its own meridian, there would be much difference in local time between one town and the other. At 10.00 a.m. in Kota Bharu (a difference of 2 and half degrees in longitude). In larger countries such as canada, U.S.A., China and U.S.S.R. the confusion arising from time differences alone would drive people mad. Travellers going from one end of the country to the other would have to keep changing their watches if they wanted to keep their appointments. This is impracticable and very inconvenient.
To avoid all these difficulties, a system of standard time is observed by all countries. Most countries adopt their standard time from the central meridian of their countries. The Nigerian government has accepted the meridian of 15 degrees east for the standard time which is one hour ahead of Greenwich Mean Time. The whole world has in fact been divided into 24 Standard Time Zones, each of which differs from the next by 15 degrees in longitude or one hour in time. Most countries adhere to this division but due to the perculiar shapes and locations of some countries, reasonable deviations from the Standard Time Zones cannot be avoided.
Larger countries like U.S.A., Canada and U.S.S.R., which have a great east-west stretch, have to adopt several time zones for practical purposes. U.S.S.R., which extends through almost 165 degrees of longitude, is divided into eleven time zones. When it is 10.00 p.m. on Monday night in Leningrad, it will be almost 7.00 a.m. the following Tuesday morning in Vladivostock. Travellers along the Trans-Siberian Railway have to adjust their watches almost a dozen times before they reach their destination. Both Canada and U.S.A. have five time zones - the Atlantic, Eastern, Central, Mountain and Pacific Time Zones. The difference between the local time of the Atlantic anad Pacific coasts is nearly five hours.