How to Determine the Time Difference Between Time Zones

The world is divided into 24 separate time zones.

The current time zone system has been in operation since 1884. Time zones are separated into 24 standard meridians of longitude which are lines running from the North Pole to the south, at right angles to the Equator. The time zones are 15 degrees apart, with the starting point prime meridian centered in Greenwich, England. The meridians are the centers of 24 standard time zones. The requirement for a standard time was encouraged in the United States and Canada, where several railway routes passed through locations that differed in local time by several hours.

Things You'll Need

• Map with world time zones

Instructions

1. Study the map and locate the destination of the required time zone.

2. Locate England on the map and look for "G" or "GMT," which stands for Greenwich Mean Time. Greenwich, London, is the starting center point of the 24 world time zones.

3. Add one hour to GMT as you pass over each time zone to the east. Subtract one hour from GMT as you pass over each time zone to the west. For example, New York is five time zones to the west of Greenwich Mean Time. Therefore, New York time is five hours behind London time.

Tips & Warnings

• A few regions use half-hour or quarter-hour differences and not one of the 24 standard time zones.

• The whole of China has decided to adopt a single time zone.

• Not all areas observe Daylight Savings Time, so take that into account when it's in effect.

• Change your watch to local time when traveling to avoid ambiguity.

References

• Travel Math: Time Difference Between Countries and Cities
• World Time Zone: World Time Zone Map
• Greenwich Mean Time: Time Zones History
• BBC KS3 Bitesize: Maths, More on Formulas, Substitution

Resources

• Time Zone Converter