» Time zone conversions

# Time zone conversions

Time zone conversions are used to convert the time in one time zone to the equivalent time in another time zone. Time zone conversions are necessary because the Earth is divided into a number of different time zones, and the time in one time zone may not be the same as the time in another time zone.

For example, suppose it is 12:00 noon in New York (Eastern Standard Time), which is in time zone UTC-05:00. In that case, it will be 11:00 am in Chicago (Central Standard Time), which is in time zone UTC-06:00. To determine the time in Chicago, you would need to convert the time in New York to the equivalent time in the Central Standard Time zone.

Time zone conversions can be done manually using a time zone converter or a world clock, or they can be done automatically using a computer or smartphone. There are also several online tools and resources available that can help you perform time zone conversions with ease.

Time zone conversions are essential for various purposes, including scheduling meetings, making travel plans, and coordinating activities with people in different time zones. They are also helpful in tracking the time of day in different parts of the world and keeping track of the time difference between the two locations.

## How to convert time

Conversion between time zones obeys the relationship

“time in zone A” − “UTC offset for zone A” = “time in zone B” − “UTC offset for zone B”,

in which each side of the equation is equivalent to UTC. (The more familiar term “UTC offset” is used here rather than the term “zone designator” used by the standard.)

The conversion equation can be rearranged to

“time in zone B” = “time in zone A” − “UTC offset for zone A” + “UTC offset for zone B”.

For example, what time is it in Los Angeles (UTC offset= −08) when the New York Stock Exchange opens at 09:30 (−05)?

time in Los Angeles = 09:30 − (−05:00) + (−08:00) = 06:30.

In Delhi (UTC offset= +5:30), the New York Stock Exchange opens at

time in Delhi = 09:30 − (−05:00) + (+5:30) = 20:00.

These calculations become more complicated near a daylight saving boundary (because the UTC offset for zone X is a function of the UTC time).