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Time Zones
Calculating Time Differences
Author:Syed Ali
Edu Level: CSEC
Date: Feb 3, 2024
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Time Zones
Across the globe is 360° (longitude) and there are 24 hours in a day thus each hour in a day is equal to 360 ÷ 24 or 15° = 1 hour. Time zones are centered around the Prime Meridian and uses Greenwich Mean Time (GMT). Greenwich is positioned at 0° splitting the globe into west and east with 180° on each side.
When calculating time, if the location is west of Greenwich the time must be subtracted but if it east of Greenwich time is added. (Again because the sun moves from east to west.)
For example, If the time in London, United Kingdom (0°) is 1:00 P.M. what is time in Port-of-Spain, Trinidad & Tobago (61° West) ?
Answer : 15° = 1 hour
at 60° = 60/15
= 4 hours
Since Trinidad is west of Greenwich the 4 hours will be subtracted therefore the time in Port-of-Spain is 9:00 P.M.
Most countries follow a timezone and larger countries may cross multiple timezones. These timezones are expressed as GMT +/- a certain amount of hours, for example Guyana is located at GMT-5 therefore one can easily tell that Jamaica is 5 hours behind Greenwich. On the other hand, Pakistan for example is at GMT+5 and is therefore 5 hours ahead of Greenwich. A map of time zones can be observed below. (Disclaimer - political changes may result in inaccuracies in some of the timezones represented below)
