Current Time in Greenwich Time Zone
IANA Name: Greenwich
Standard Offset: UTC +00:00
Daylight Saving: No
Currently Observing DST: No ❌
Greenwich Mean Time (GMT): The World's Timekeeping Zero Point
Greenwich Mean Time (GMT), designated as UTC+00:00, is the time zone anchored at the Royal Observatory in Greenwich, London. It serves as the world's prime meridian and the baseline from which all other time zones are measured. This zone does not observe daylight saving time, remaining constant throughout the year. It is used by several countries in West Africa and a few Atlantic islands, as well as by the United Kingdom during winter months (though the UK switches to British Summer Time in summer).
Overview and Scope
The IANA time zone Europe/London is the canonical zone for Greenwich, but the offset UTC+00:00 (GMT) is shared by many other zones. The GMT offset is used year-round in countries such as Ivory Coast (Africa/Abidjan), Ghana (Africa/Accra), Mali (Africa/Bamako), Gambia (Africa/Banjul), Guinea-Bissau (Africa/Bissau), Guinea (Africa/Conakry), Senegal (Africa/Dakar), Sierra Leone (Africa/Freetown), Togo (Africa/Lome), Liberia (Africa/Monrovia), Mauritania (Africa/Nouakchott), and Burkina Faso (Africa/Ouagadougou). Additionally, the Atlantic islands of Iceland (Atlantic/Reykjavik) and the Faroe Islands (Atlantic/Faroe) also use GMT year-round, though the Faroes observe summer time. The offset is also used in the British Overseas Territories like St Helena and Ascension Island.
Offset and Abbreviation
The standard offset is UTC+00:00, meaning local time is exactly Coordinated Universal Time (UTC) with no addition or subtraction. The abbreviation GMT stands for Greenwich Mean Time, historically referring to the mean solar time at the Royal Observatory. In practice, GMT is synonymous with UTC for civil timekeeping. The abbreviation is used in many contexts, including aviation, broadcasting, and international coordination.
Daylight Saving Time (DST) Behaviour
Greenwich itself, as part of the United Kingdom, observes British Summer Time (BST, UTC+01:00) from the last Sunday in March to the last Sunday in October. However, the Europe/London zone switches between GMT (UTC+00:00) in winter and BST (UTC+01:00) in summer. This article focuses on the GMT offset specifically, which is constant year-round in the West African countries listed. Those countries do not observe DST, so their clocks never change. For example, Accra, Ghana, remains at UTC+00:00 all year, while London shifts to UTC+01:00 in summer. This means that during British Summer Time, London is one hour ahead of Accra.
Main Countries and Cities
- United Kingdom (winter only): London, Edinburgh, Cardiff, Belfast (switch to BST in summer).
- Ireland (winter only): Dublin (switches to IST, UTC+01:00 in summer).
- Portugal (winter only): Lisbon, Porto (switches to WEST, UTC+01:00 in summer).
- Canary Islands (Spain, winter only): Las Palmas, Santa Cruz (switches to WEST in summer).
- Ivory Coast: Abidjan, Yamoussoukro.
- Ghana: Accra, Kumasi.
- Mali: Bamako.
- Senegal: Dakar.
- Burkina Faso: Ouagadougou.
- Iceland: Reykjavik.
- Liberia: Monrovia.
- Mauritania: Nouakchott.
- Guinea: Conakry.
- Gambia: Banjul.
- Sierra Leone: Freetown.
- Togo: Lome.
- Guinea-Bissau: Bissau.
Business Hours and Scheduling Calls
Because GMT does not observe DST, scheduling with regions that do requires careful attention to seasonal shifts. For example, during winter, London and Accra are both at UTC+00:00, so a 9 AM meeting in London is also 9 AM in Accra. But in summer, London moves to UTC+01:00, so 9 AM in London is 8 AM in Accra. When calling from New York (Eastern Time, UTC-05:00 in winter, UTC-04:00 in summer), the difference to GMT is 5 hours in winter and 4 hours in summer. For instance, 12 PM GMT is 7 AM EST in winter and 8 AM EDT in summer. Business hours overlap well with West Africa: typical work hours (9 AM to 5 PM GMT) align with late morning to early evening in the Americas and late afternoon to night in Asia. For example, 2 PM GMT is 9 AM in New York (EST) and 10 PM in Tokyo (JST).
Frequently Asked Questions
What is the difference between GMT and UTC?
GMT (Greenwich Mean Time) is a time zone based on the mean solar time at the Royal Observatory in Greenwich. UTC (Coordinated Universal Time) is an atomic time standard that is extremely precise. For civil timekeeping, they are effectively the same, with no difference in offset. GMT is often used as a time zone name, while UTC is the standard reference.
Does Greenwich observe daylight saving time?
Greenwich itself, as part of the United Kingdom, does observe daylight saving time (British Summer Time, BST, UTC+01:00) from the last Sunday in March to the last Sunday in October. However, the GMT offset (UTC+00:00) is used year-round in many countries in West Africa and a few other regions that do not observe DST.
Which countries use GMT year-round without DST?
Countries that use GMT (UTC+00:00) year-round include Ivory Coast, Ghana, Mali, Senegal, Burkina Faso, Iceland, Liberia, Mauritania, Guinea, Gambia, Sierra Leone, Togo, Guinea-Bissau, and the Atlantic islands of St Helena and Ascension. These nations do not change their clocks for daylight saving.
What is the time difference between GMT and Eastern Standard Time?
Eastern Standard Time (EST) is UTC-05:00, so GMT is 5 hours ahead of EST. For example, 12:00 PM GMT is 7:00 AM EST. During Eastern Daylight Time (EDT, UTC-04:00), the difference is 4 hours (12:00 PM GMT is 8:00 AM EDT).
Why is Greenwich Mean Time called the 'prime meridian'?
The prime meridian is the line of 0 degrees longitude, which passes through the Royal Observatory in Greenwich. It was established as the international standard for longitude and timekeeping at the International Meridian Conference in 1884. All time zones are defined by their offset from this meridian.
How do I convert GMT to my local time?
To convert GMT to your local time, find your time zone's offset from UTC. If your offset is, for example, UTC+05:30 (India), then your local time is GMT plus 5 hours 30 minutes. If your offset is UTC-03:00 (Argentina), then local time is GMT minus 3 hours. Remember to account for daylight saving if your region observes it.