The Greenwich Mean Time and its history

Greenwich Meridian

Nowadays we have the luxury of being able to keep time with our smartphones, smartwatches, and many other devices in our home. However, what was it like a few centuries ago? Did you ever wonder what’s the difference between UTC and GMT? These 2 timezone systems are very similar, but yet, so different. We gathered all the information you’ll ever need about the history of the Greenwich Mean Time.

What’s GMT exactly?

GMT stands for Greenwich Mean Time and is a timezone system that was invented in the 1800s. To be more precise, it is astronomer Royal George Biddell Airy who, in 1884, had the brilliant idea to extend the concept of the timezone table that had been created in 1879 by Sir Standford Fleming.

You see, with the time zones, travelers and cargo ships were able to adjust time consequently but there was still a huge problem that was persisting since the 1700s: the longitude. The problem was that with no point of reference to find their longitude, cargo ship crews could easily get lost on long travels since the sun was changing positions between time zones at different times.

Therefore, the main idea of the Greenwich MeanTime (GMT) from Mr. Biddel Airy was to have a point of reference that everybody could easily use that would show 0° longitude. That way, traveling from one timezone to another would be much easier and a lot safer for not only the crews, but also what the ships are transporting as well.

Why is it called Greenwich Mean Time?

To find the 0° longitude that everybody would use as a point of reference, astronomers of the 1800s used one of the best clocks in the world. This clock was located in the small town of Greenwich in England. This village is located not too far from London actually and houses the Royal Observatory of Greenwich.

This is also where the 0° longitude is located, you can even walk on it, jump on either side of the latter if you feel like it, as there is a big line fixed on the ground near the Observatory to show you the 0° longitude in all its glory.

Is Mean Time better than Solar Time?

When we speak of Solar Time, we are talking about ancient systems where, for example, Egyptians would use the position of the sun and calculate how much time it takes the sun to cross the highest point in the sky. This way of calculating time always varies depending on the seasons and your location, so it’s really not precise. So that being said, Mean Time is much better because it relatively stays the same no matter where you are located in the world. The results are constant in a certain way and don’t rely on whether or not there will be clouds hiding the sun during the day.

Why did Greenwich Mean Time (GMT) get replaced?

It is important to understand the main difference between UTC (Coordinated Universal Time) and GMT (Greenwich Mean Time). There is a major reason why a new and more modern time zone system had to be invented because it turns out that there are too many variables with GMT.

That’s right since GMT relies on the Sun position when crossing the Prime Meridian (0° longitude), it means that it will never give perfect results. That is due to the fact that the planet Earth is not rotating around the sun in a perfect circle. Additionally, Earth is not a perfect sphere. These 2 elements induce quite a big deal of variables into the equations used to calculate time.

On the other hand, UTC doesn’t rely at all on the position of the sun and doesn’t even use the Prime Meridian. In fact, it uses extremely precise atomic clocks that use quartz oscillators that send certain frequencies to a bunch of atoms. These atomic clocks were invented by NASA since the teams over there needed precise time information when running space operations.

These clocks are now used all around the world without most people even knowing the chance that they have to be able to have such a tool in their everyday lives. Moreover, UTC replaced GMT in most countries, nevertheless, some still use GMT.

Does UTC use Day Saving Time?

No, UTC doesn’t use Day Saving Time since it doesn’t rely on the Earth and Sun positions. UTC only relies on its atomic clock system which always gives the same constant precise results. In some countries, however, Day Saving Time DST is still used as a way to ‘calibrate’ time through the seasons.

For example, in Canada, Daylight Saving Time begins in March and ends in November. In March, all clocks in Canada will go forward 1 hour, and all clocks in November go back 1 hour. This is needed in order to have more sunlight during summer, but also to save electricity during winter where it’s a lot colder at night.

In what country GMT is still used in 2021?

Since UTC has replaced GMT in many countries, it is normal to wonder if any countries in the world are still using the old Greenwich Time system. Here’s a list of them below:

  • Australia
  • Ireland
  • Malaysia
  • India
  • Iceland
  • Pakistan
  • South Africa
  • Greenland
  • Isle of Man
  • New Zealand
  • United Kingdom

Finally, it’s important to note that it doesn’t really matter if a country is using GMT or UTC. Since both timezone systems are quite similar on a fundamental basis (both of them are divided into 24 equal parts), it means that you don’t worry whether or not your device is showing the right time.

In conclusion, we could say that we are pretty lucky to have so many advanced technologies at our disposal and that we don’t have to deal with the position of the sun anymore to know what time it is or where we are located in the ocean. That said, not only do some countries still use GMT but also some important entities in the world, such as the US military and the Royal Navy.

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