UTC offset


The UTC offset is the difference in hours and minutes between Coordinated Universal Time (UTC) and local solar time, at a particular place. This difference is expressed with respect to UTC and is generally shown in the format ±[hh]:[mm], ±[hh][mm], or ±[hh]. So if the time being described is two hours ahead of UTC (such as in Kigali, Rwanda [approx. 30° E]), the UTC offset would be "+02:00", "+0200", or simply "+02".

By convention, every inhabited place in the world has a UTC offset that is a multiple of 15 minutes but the majority of offsets are stated in whole hours. There are many cases where the national standard time uses a time zone that differs from the UTC offset appropriate to its longitude.

Time zones and time offsets

World map of current time zones

A time zone is a geographical region in which residents observe the same standard time. Although nominally a new time zone is established every 15 degrees east or west of the prime meridian (meaning a one hour change in solar time), in practice local geographical or political considerations may vary its application. The most extreme example of this is time in China, which applies a single standard time offset of UTC+08:00 (eight hours ahead of Coordinated Universal Time), even though China spans five geographical time zones.

The UTC offset (or time offset) is an amount of time subtracted from or added to Coordinated Universal Time (UTC) time to specify the local solar time (which may not be the current civil time, whether it is standard time or daylight saving time).

Daylight saving time

Several regions of the world use daylight saving time (DST) and the UTC offset during this season is typically obtained by adding one hour to local standard time. Central European Time UTC+01:00 is replaced by Central European Summer Time UTC+02:00, and Pacific Standard Time UTC−08:00 is replaced by Pacific Daylight Time UTC−07:00.

Notable examples

These cities have been chosen for convenience because they are sufficiently near the equator so as not to use DST.

Some example cities
Location Longitude UTC offset When UTC time is 12:00,
local standard time is:
When local time is 12:00,
UTC time is
Honolulu, USA 157º 51 W UTC-10:00 02:00 22:00
Quito, Ecuador 78º 30' W UTC-05:00 07:00 17:00
Accra, Ghana 0º 12' W UTC+00:00 12:00 12:00
Colombo, Sri Lanka 79º 50' E UTC+05:30 17:30 06:30
Darwin, Australia 130º 30' E UTC+09:30 21:30 02:30

See also

  • ISO 8601 – international standard for representing dates and times.

External links

  • Time Service Dept., U.S. Naval Observatory