London uses Greenwich Mean Time (GMT) during standard time and
GMT was ultimately adopted across Great Britain by the Railway Clearing House in December 1847. It officially became 'Railway Time'. By the mid-1850s, almost all public clocks in Britain were set to Greenwich Mean Time and it finally became Britain's legal standard time in 1880.
UTC is 1 hour behind London.
Only 1 nationwide time zone
GMT corresponds to Coordinated Universal Time (UTC+0:00), which is the worldwide reference for timekeeping. However, during the summer months, people switch to British Summer Time (BST), which corresponds to UTC+1:00.
Coordinated Universal Time
Although both GMT and UTC display the same time, there is a difference: GMT is now considered just a time zone officially used in some European and African countries. But UTC is not a time zone, but rather the new time standard that is the basis for clock time and time zones worldwide.
How Many Time Zones Are There in the UK? The United Kingdom has one standard time zone. The overseas territories and crown dependencies of the UK bring the total to 9 time zones.
During the Second World War, in 1941 Britain adopted British Double Summer Time, which saw clocks being put forward two hours ahead of GMT. The clocks were turned back to GMT at the end of summer 1945.
British Summer Time is a mechanism to make the most of increased summer daylight hours in the northern hemisphere.
London is on Greenwich Mean Time (GMT) only during winter months. The GMT time zone has the same hour offset (GMT+0) as the Western European Standard Time Zone. When Daylight Saving Time starts, London and the whole of UK are on British Summer Time (BST), which is GMT+1.
It remained the standard until 1972 when it was replaced with Coordinated Universal Time (UTC). UTC is still primarily based on the solar time on the prime meridian (0° longitude) near the Royal Observatory in Greenwich.
There were two main reasons for the choice. The first was the fact that the USA had already chosen Greenwich as the basis for its own national time zone system. The second was that in the late 19th century, 72% of the world's commerce depended on sea-charts which used Greenwich as the Prime Meridian.
With a land mass close to 7.7 million square kilometres, Australia is the world's sixth largest country and is divided into three separate time zones.
France, Holland, Luxembourg and Belgium were all originally in the same time zone as the UK, but Germany changed their time to match the German zone (one hour ahead of the UK) during their occupation of those countries during the war.
Iceland, Ireland, and the United Kingdom observe GMT as their standard time. Iceland does not observe DST so it remains on GMT all year round.
Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, counted from midnight.
Australia uses three main time zones: Australian Eastern Standard Time (AEST; UTC+10:00), Australian Central Standard Time (ACST; UTC+09:30) and Australian Western Standard Time (AWST; UTC+08:00). Time is regulated by the individual state governments, some of which observe daylight saving time (DST).
How Many Time Zones Are There in the UK? The United Kingdom has one standard time zone. The overseas territories and crown dependencies of the UK bring the total to 9 time zones.
Greenwich Mean Time (often called GMT) is the clock time at the Royal Observatory in Greenwich in London. The Shepherd gate clock, which can be seen at the Royal Observatory's gates, is the first clock to ever display GMT to the public. Greenwich Mean Time is calculated by using the sun.
Although there was GMT, a committee at the United Nations officially adopted UTC as a standard. This is because it is more accurate than GMT for setting clocks.
The United Kingdom time zone is called GMT (Greenwich Mean Time) on Outlook. GMT is the time zone of the 0° longitude and is used as the international time standard. It is also known as UTC (Coordinated Universal Time).
All time zones are defined by their offset from UTC. The offset is expressed as either UTC- or UTC+ and the number of hours and minutes. Primarily, UTC is based on mean solar time at the prime meridian running through Greenwich, UK. For every 15 degrees of longitude east or west, mean solar time changes by 1 hour.
Prior to 1972, this time was called Greenwich Mean Time (GMT) but is now referred to as Coordinated Universal Time or Universal Time Coordinated (UTC). It is a coordinated time scale, maintained by the Bureau International des Poids et Mesures (BIPM).