Greenwich mean time, or GMT for short, was the world’s first proper timezone. It became the time zone that every other time zone in the world is based on in 1884. But, which countries have the GMT timezone?
The United Kingdom and Ireland are the main countries where GMT is used. However, the timezone is also used in most of Portugal, Ghana, Togo, Senegal, and many more.
It is worth noting that many countries do not explicitly refer to it as GMT. Nowadays, many countries refer to it as UTC. On this page, we wish to give you a bit more information on the GMT time zone.
Which Countries Have The GMT Time Zone?
Twenty countries have the GMT time zone:
- The United Kingdom (includes Crown Dependencies of Jersey, Isle of Man, and Guernsey)
- Ireland
- Portugal (except the Azores in the Atlantic Ocean)
- Faroe Islands
- Canary Islands
- Togo
- Senegal
- Sierra Leone
- Burkina Faso
- Guinea
- Ghana
- The Gambia
- Guinea-Bissau
- Iceland
- Ivory Coast
- Liberia
- Mali
- Mauritania
- Sahrawi Arab Democratic Republic
- Saint Helena, Ascent, and Tristan da Cunha
Do bear in mind that there are some countries on the same longitude as the UK e.g. France that will not use GMT. Instead, they use UTC+1 to put them in line with the other countries on the continent. The one exception to this rule is Portugal which, instead, has opted to stick to GMT.
While not a country, Antarctica also uses GMT, due to a British scientific and research base there.
Do Countries In The GMT Time Zone Have Daylight Saving Time?
Only five countries in GMT use DST:
- The United Kingdom
- Ireland
- Portugal (except the Azores in the Atlantic Ocean)
- Faroe Islands
- Canary Islands
In the summertime, the UK switches to British Summer Time (BST). This is GMT+1. If you are in the UK, then you will likely always see it referred to as BST when required. However, in most cases, the exact time zone will not be specified. Outside of the UK, countries may refer to their DST as different names.
The other countries that use GMT do not need to do so. Most of them are close to the equator, and thus there is no need for them to have DST. Their daylight does not change throughout the year. Other countries have simply opted not to use it, whether it is for practical purposes or due to how other countries close by are operating.
Is GMT The Same As UTC?
Yes. UTC is the same as GMT (most of the time). Many people see UTC as the successor to GMT. In fact, GMT (outside of daylight saving time) is UTC+0.
Do bear in mind that there is a slight difference between the two. Depending on where you are in the time zone, UTC can be as much as 0.9 seconds in front of GMT. However, for all intents and purposes, the UTC and GMT timezone names can be directly comparable. It is rare that the average person will need to be specific about whether they are talking about UTC or GMT.
In British law, UTC is not defined as the official time zone for the country. Instead, it is defined as Greenwich mean time. This means any references to time within the UK will be on GMT instead.
The History of GMT
GMT, as a time zone, began as a navigational exercise. Sailors would determine longitude to help map waters and land. At the time, these sailors would use the solar time to calculate the time of day. This essentially meant they were looking at the position of the sun in the sky.
In the UK, the Prime Meridian ran straight through the Royal Observatory in Greenwich, London. This line is rather arbitrary and, in theory, it could be placed anywhere on earth. There were multiple prime meridian lines, but it is the one in the UK that won out.
The prime meridian line is essentially 0 degrees on the longitude line. Sailors would have a device on board their ship known as a chronometer. This chronometer would allow sailors to determine the time difference between the prime meridian line and their current location. The time at their current location could be determined not only by looking at the sun but by the observation of celestial bodies i.e. stars.
Over time, the sailors and scientists realized that this method of tracking the time was fantastic. No matter where you were on the planet, you could always calculate how different your time was from that at the prime meridian. So, if the celestial bodies were 1 hour behind what would be observed at the prime meridian, then you know you were in GMT-1.
Eventually, the United Kingdom decided to adopt GMT as the timezone in the UK. This happened in 1847, but, back then, some referred to it as railway time (as it was first applied to the railways, some of which still refer to it as such in the UK).
By 1884, the world had essentially agreed to adopt GMT as the standard base timezone, and every country’s time zone would be based upon whatever the time was in Greenwich.
This continued up until 1960 when it was determined that GMT wasn’t quite accurate enough for some purposes. As a result, every country in the world started to coordinate using UTC instead.
Many countries, even if they do not use GMT, still refer to GMT in law e.g. in Belgium, the time zone is technically based on GMT (they operate on GMT+1), while Canada has numerous references to GMT in their legislation.
Final Thoughts
There are many countries in the GMT time zone, with the most populated of these being the United Kingdom, Ireland, and Portugal. GMT is virtually comparable to UTC+0. So, you can also say that these countries are located in UTC+0 too unless you need to be hyper-specific about the time zones, although that is only required for scientific purposes.
