#Gmt is what time zone portable#

Some British clocks from this period have two minute hands, one for the local time and one for GMT. By 1855, 98% of Great Britain's public clocks were using GMT, but it was not made the island's legal time until August 2, 1880. This practice was soon followed by other railway companies in Great Britain and became known as Railway Time.Īround August 23, 1852, time signals were first transmitted by telegraph from the Royal Observatory.

#Gmt is what time zone portable#

In November 1840, the British Great Western Railway started using GMT kept by portable chronometers. In the 19th century, as transportation and telecommunications improved, it became increasingly inconvenient for each location to observe its own solar time. Main article: Railway time Plaque commemorating the Railway General Time Convention of 1883 in North America The control panel of the Time Zone Clock in front of Coventry Transport Museum DST is usually used for about half of the year, typically by adding one hour to local time during spring and summer. The UTC offsets range from UTC−12:00 to UTC+14:00, and are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes (such as in India, South Australia and Nepal).Īreas of extreme latitude are more likely to use DST.

Some time zones switch between offsets throughout the year due to daylight saving time (DST). Time zones are defined as one or two offsets from Coordinated Universal Time (UTC), and (if two offsets are used) the days when the offset changes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time. For other uses, see Time zone (disambiguation).Ī time zone is an area which observes a uniform standard time for legal, commercial and social purposes. For more time zone lists, see Lists of time zones. For a list of time zones by country, see List of time zones by country. Next time change is highlighted.This article is about time zones in general. Time Changes in London Over the Yearsĭaylight Saving Time (DST) changes do not necessarily occur on the same date every year. Some other countries, such as Ireland, observe the same local time, but under a different name. The UK is the only country that observes BST in the summer. What About BST?ĭuring Daylight Saving Time, clocks in the United Kingdom are set forward one hour to British Summer Time (BST). Until 1972, time zones were defined by their offset from GMT based on mean solar time at the prime meridian in Greenwich near London.

GMT is a time zone used in the UK and other European and African countries.Ī source of confusion is that GMT used to be the world's time standard before UTC was introduced.

Since GMT has a UTC offset of zero, there is no time difference between the two. Time zones are defined by their offsets from UTC.

UTC is a time standard that forms the base of time zones worldwide and is not used as a time zone in any country.

However, there is an essential difference between the two: In practice, GMT and UTC share the same time on a clock, which can cause them to be interchanged or confused. London uses Greenwich Mean Time (GMT) during standard time and British Summer Time (BST) during Daylight Saving Time (DST), or summer time. The graph above illustrates clock changes in London during 2024. Business Date to Date (exclude holidays).