UTC Time – Coordinated Universal Time


When it comes to understanding world time, most people don’t know what UTC is and what the UTC time. Curiously, UTC is both a time standard and a time zone, and it’s frequently used to describe either… Confused yet? To shed light on the matter, let’s talk about what time zones really are, what UTC is, and what are some of the major countries and cities in UTC. 

Understanding time zones and the UTC time standard is essential if you’re traveling if you work with people in different countries, or simply for social reasons. For example, if you’re based in London, UK, and you’re calling someone in Los Angeles, US, keep in mind they’re eight hours behind you. This means that if you’re trying to reach them at 10 AM your time, you’re calling them at 2 in the morning in LA! Needless to say, your Los Angeles friend won’t be happy to answer that call.

In addition to time zone confusion, UTC is often used instead of GMT, the Greenwich Mean Time. To find out why and to learn some fun time zone facts to outshine your trivia night rivals, let’s dig into the history, use, and curious facts about the UTC and time zones in general.

What Is a Time Zone?

A time zone is a region on Earth that observes the same time. This way, it will be the same hour in all the countries and the cities in the particular time zone they observe. Time zones run horizontally rather than vertically: Moscow and Paris will have different time zones, but Cape Town and Madrid observe the same time. This is because time zones aren’t about longitude but rather, latitude due to the rotation of the Earth. 

As you can imagine, noon is at different times in each country, which means that noon (12 PM) would be observed at different times from country to country corresponding to their position West or East. Without a standard time that all countries in a time zone must observe, the countries would never observe at the same time. 

Imagine the chaos this would cause: without agreeing on standard time, we wouldn’t be able to agree on, well, anything else. Time zones are very important for commercial and social activities, legal reasons, military use, trade, and just about every other human activity on the planet. 

As long as two countries are in the same time zone, you won’t have any communication issues. If the person you are speaking to or who ships your product is in a different time zone, it may be midnight your time when it’s noon his or her time. You can imagine the trouble you would have communicating with people who are 6 to 12 hours ahead or behind your time! This is where time zones come in: you can plan your communication by calculating the time differences between you and the person you’re trying to reach, and suggest a time that suits you both.

In addition, time zones are very important for military purposes. The military uses different names for the different time zones, but the way they work is exactly the same. For example, UTC is Zulu Time in military jargon.

Finally, time zones matter when it comes to legal issues and work contracts. If you live in Seattle and you’ve promised to deliver a certain project to an Ireland-based company by, say, Monday morning, you better get it done on Sunday evening your time – Seattle is eight hours behind Dublin, which means your today is their tomorrow and, unless agreed otherwise, they will be expecting results on their time – not yours.

What Is UTC?

UTC stands for Coordinated Universal Time. This is the primary time standard in the world, and the standard after which the entire world regulates its time. Your clock is regulated by the Coordinated Universal Time standard. 

UTC is not a time zone, even though people use it as one. Again, UTC is a time standard. UTC has a difference of less than one second of mean solar time at a longitude of 0 degrees. In other words, UTC is, in essence, the „zero hour“ time. 

Even though this time standard came to use from the start of 1960, it was officially adopted a little later, in 1967. Of course, the time standard has undergone several adjustments over time, and the UTC we use today was implemented in 1972.

It contains what is called “leap seconds,” which makes it easy to adjust the time in the future if need be. Why adjust the UTC in the first place? This is because of irregularities in the Earth’s rotation rate. Because of this irregular rotation rate, UTC is slowly drifting away from the extremely precise atomic time. As such, it needs to be adjusted periodically. 

Depending on where you live, your country probably observes Daylight Saving Time (DST) moving one hour back or forth in the spring and the fall. UTC, however, is not affected by this and it will never change for DST. Essentially, UTC is the one unmovable time standard that will not change under any circumstances, except the minor lea second adjustments to account for precise atomic time.

Brief History of UTC

The history of UTC dates back to 1884 when the International Meridian Conference was held in Washington D.C. It was indeed one of the most important events in the history of the timezone adaptation. In fact, that’s when the 24-hour time zone system was first introduced. The representatives of the countries who attended the conference decided to choose a particular time for global use. By this time, having different time systems was a severe problem for worldwide travel, communication, economy, and politics. Therefore, establishing a global timezone system seemed like a rational step for everybody. 

The representatives of different countries determined the Royal Observatory in Greenwich, London as the starting point of calculating the time and called it the Prime Meridian. Many cities quickly followed the change and switched to one of the five one-hour wide time zones across the continent. 1884 was the exact time when the Universal Time or UT started functioning as well.

Nowadays people often confuse UTC and GMT with each other and use these two terms interchangeably. While at a first glance they are pretty much alike, actually, these two terms are not completely the same. They are technically the same but they describe the different time-related features. We’ll describe the difference below and keep on focusing on the history of the Universal Time for now. 

Although Greenwich meridian was selected as the Prime Meridian, from the 1950s the world switched to using GMT as the new time standard. However, soon it became obvious that there were more effective ways for measuring the time. With the invention of atomic clocks in the 20th century, using solar time for calculating the time wasn’t satisfying anymore. As a result, at the beginning of 1960, the world started using the new standard for coordinated time. 

Coordinated Universal Time (UTC) was first introduced on January 1, 1960. However, it became an official term only in 1967 by the International Radio Consultative Committee and replaced GMT a year later. On January 1, 1972, UTC was adjusted by adding “leap seconds” – one-second adjustment for accommodating the difference between precise time and observed solar time. Today’s UTC is in line with the Earth’s rotation. Still, it’s not entirely even but it’s the most optimal way to calculate the time up to now. 

UTC and Greenwich Mean Time: The Differences

Many people say that they live in the UTC time zone. While it may make sense in casual day to day use, this is, in fact, an incorrect statement. Why? Because UTC is a time standard rather than a time zone. 

What they should be saying instead is that they live in the GMT time zone. GMT, an abbreviation for Greenwich Time Zone, is the time zone that observes UTC+00:00 time (exact UTC time). GMT was established in 1675 by the Royal Observatory in Greenwich, UK, to define the mean solar time in this precise location. This was done to help British sailors figure out the longitude from the Greenwich meridian (zero degrees) while at sea, giving them a standard reference time. In 1884, it was adopted as a standard at the International Meridian Conference, and it gave base to time zones as we know them today. From maritime use, the GMT was next adopted by the British railway system, then Ireland, and eventually, the entire world. However, GMT is not as precise as the UTC, and that’s why it has been replaced by the UTC standard. GMT is now firmly a time zone, whereas the UTC stands for the universal standard.

So how does it work today?

The plus sign in the +00:00 UTC is known as the offset from Coordinated Universal Time. It tells people by how many hours their time is offset from UTC. For example, the United States is in several time zones: Colorado is in UTC-07:00, while California, Nevada and Oregon are in UTC-08:00. Samoa, in contrast, has a time offset of UTC+13:00; Baker Island and Howland Island, on the other hand, have a negative offset of UTC-12:00. 

Once again, time zones aren’t about geographical locations based on their position of North vs South or international country boundaries but rather, the West-East coordination: the same country can have several different time zones, but one time zone may apply to several different countries. To make this easier, think of it this way: if you can draw a vertical line across the map, the countries on that line will share the same time zone. However, if you draw a horizontal line from West to East, the countries on the line will be in different time zones.

The differences in time between various countries on Earth can be huge, and some countries like Russia have as many as eleven time zones within their territory. On the other hand, some countries, despite their gargantuan size and millions of inhabitants, refuse to observe different time zones: India, as an example, observes just one time zone, the GMT +5:30. Although different regions in India had kept different time zones before, their time zones were unified during the colonial era to better manage the railway system. For better or worse, the unified time zone stuck, and Indians now observe the same time whether they live in Kmombai or Kolkata. Another example is China: although its immensely vast territory spans at least five geographical time zones, China only observes the UTC+08:00 time zone, or the Beijing time. It’s a little like trying to keep the same time regardless of whether you’re in Arizona or New York, but, surprisingly enough, the Chinese seem to manage just fine.

In addition to these oddities,  keep in mind that the GMT time zone, much like the UTC time standard, will never change for DST (Daylight Saving Time). However, some countries that observe DST will switch to a different time zone for this purpose. For example, the United Kingdom (who established GMT) switches to BST (or British Summer Time) during the summer months. As you might have guessed, BST time is 1 hour ahead of GMT time.

On the other hand, plenty of countries around the world do not bother to switch back and forth to the DST. Several South American countries such as Argentina and Peru as well as Asian countries like Thailand, Japan, and China, and most African countries do not change to DST and keep their time still – pun intended. Equally, some regions of the same country may or may not observe DST – for example, South Australia is on board with the DST changes, while Western Australia and Queensland are not.

How to Convert UTC to Other Time Zones?

Converting Coordinated Universal Time to other time zones and adjusting it to your local time is nothing difficult. For this, you just need to understand the basic principles of time conversion. But don’t worry if you find them too complicated because today there are many simple online tools in order to help people convert UTC to various time zones. 

First of all, you should understand that the world is divided into 24 time zones. However, this number is not 100% correct because some states and regions usually shift their times by half an hour from the 24-hour divisions. Still, Standard time is generally a whole number of hours from the UTC. The worldwide standard time is based on the work of atomic clocks that are kept at various laboratories around the world to maintain the time. 

Use the following guideline in order to convert UTC in different time zones:

  • Coordinated Universal Time (UTC) is 4 hours ahead of Eastern Time (EST)
  • Coordinated Universal Time (UTC) is 6 hours ahead of Central Standard Time (CST).
  • Coordinated Universal Time (UTC) is 6 hours ahead of Mountain Standard Time (MST).
  • Coordinated Universal Time (UTC) is 7 hours ahead of Pacific Time (PST).

Major Countries in the GMT Time Zone (Using Coordinated Universal Time)

Many countries in Europe and Africa have an offset of UTC+00:00. This means that they are in the GMT time zone. Here are the countries that use standard time all year round:

  • Burkina Faso in Africa
  • The Gambia in Africa
  • Mauritania in Africa
  • Ghana in Africa
  • Côte d’Ivoire in Africa
  • Guinea in Africa
  • Liberia in Africa
  • Mali in Africa
  • Senegal in Africa
  • Guinea-Bissau in Africa
  • Sierra Leone in Africa
  • Togo in Africa

There are also some Atlantic Islands:

  • Greenland
  • Iceland
  • Saint Helena
  • Ascension Island
  • Tristan da Cunha

In Europe, the following territories are in the GMT time zone, but only in the Northern Hemisphere winter period:

  • Alderney
  • United Kingdom
  • Guernsey
  • Sark
  • Faroe Islands
  • Herm
  • Isle of Man
  • Jersey
  • Ireland
  • Portugal (remember that the Azores area has an offset of UTC−01:00)

Although there are no official figures, the number of people who live in the GMT time zone is in the hundreds of millions. 

Important Cities in UTC

As you can imagine, there are a lot of major cities in the GMT time zone (observing UTC time). However, keep in mind that many of these cities are not observing UTC time all year round because of Daylight Saving Time and other time zone adjustments. Here are the major cities that observe UTC at one time or another during the year:

Problems with UTC

Even though UTC is a worldwide standard, it’s not an entirely ideal time system. In fact, Coordinated Universal Time is accompanied by some problems such as leap seconds or other issues. Therefore, it offers useful information which can be rather limited sometimes. Let’s dive deeper into the problems of UTC.

Leap Seconds

“Leap Seconds” is one of the biggest problems with the global use of UTC. As we already mentioned, it’s a one-second adjustment that is applied to the Coordinated Universal Time from time to time. The purpose of these seconds is to adjust the difference between the time measured by “atomic clocks” and observed solar time known as UT1. 

Usually, the Earth doesn’t move absolutely regularly and UT1 varies due to the changes in the Earth’s movements. Leap seconds are important for UTC to get ahead of observable solar time. This means that 0.9 is the maximum difference between the UTC and the solar time. This measurement is done by the International Earth Rotation and Reference Systems Service (IERS)  but it’s not entirely accurate which is why it’s considered a problem with UTC.

  • Observing daylight saving time (DST) in the cases of some countries is another problem related to UTC. While some countries stopped using daylight saving time, you still need to know the exact location with others in order to find out the accurate time. The reason is that some regions like Navajo Nation, in northeastern Arizona, still use DST. 
  • The date is interpreted differently by various calendars. Specifically, in the 16th century the world began using the Gregorian calendar which is used up to now but before, people used the Julian calendar for determining time and date. Therefore, sometimes interpreting the date universally can be problematic. 
  • Different countries started using UTC at different times. Therefore, if you want to determine the time in the past, you’re highly likely to encounter some issues.

Use of UTC

After all this discussion about the UTC, now it’s finally to state who actually uses Coordinated Universal Time. Surprisingly, people don’t directly use UTC. Generally, most people live in locations where time is calculated based on GMT and not UTC. But then, why do we need UTC after all?

The answer is very simple. UTC is the term mainly adjusted for the World Wide Web standards. The Network Time Protocol (NTP) is a system for clock synchronization between computer systems that has operated since 1985. The Protocol, which is now the oldest Internet protocol still used, uses information from the UTC system for transmitting the time. 

Besides, UTC is the time standard in aviation. Usually, maps, weather forecasts, flight plans, or air traffic control are based on the UTC. It’s important to avoid confusion about various time zones when airplanes move from one time zone to another.

Interesting Time Zone Facts

Even though UTC is a time standard and GMT is a time zone, UTC is often being used even by official sources. It is expected, in fact, that UTC will replace GMT in the near future. So, all things considered, it’s not a big mistake to say that you are in a UTC time zone – as long as you keep the right time!

Now that you know what Coordinated Universal Time is and where it applies, let’s take a look at some interesting time zone facts:

  • Most time zones are offset from UTC using whole hours. However, there are countries that have offsets that contain parts of an hour. For example, India is in UTC+05:30. Also, the Nepal Standard Time is basically UTC+05:45. Talk about attention to details!
  • There are proposals to replace the UTC with another standard – one that does not use leap seconds to adjust the time after the atomic clock time. 
  • The first leap second was added on June 30, 1972. In total, there have been 27 seconds added to UTC over the years, up to date.
  • The length of the mean solar day is increasing because the Earth’s rotational speed is slowly decreasing because of the tidal deceleration effect. Time to slow down, folks.
  • The Earth will keep slowing down its rotation, so more and more leap seconds will be added in the future to compensate.
  • Daylight saving time was created to help people enjoy more active hours during daylight… but most people still report feeling somewhat groggy and confused on the first few days after the DST change!
  • The differences in time zone have an interesting effect. While it may be Monday where you live, it may be Tuesday or even Sunday where the person you are talking to lives. In other words, your today is somebody’s tomorrow, and someone’s yesterday may be your now. 
  • It’s easy to forget about time zones when travelling by plane over long distances. Be careful not to call somebody at 3 in the morning thinking it’s 10 AM there as well!
  • Both cell phones and computers adjust time automatically when you travel from one time zone to another. But you will have to manually adjust your watch.
  • Did you know that you can have two birthdays? Just take a plane to another time zone and you can turn your clock back by anywhere from 3 to 12 hours.

So there you have it: UTC and time zones may be confusing at first, but once you figure out how standard time works, it’s just a matter of calculating the differences between the hours ahead or behind. And if you don’t have the time to check the hours, just use this simple time zone converter to check time in different countries around the world.