It all started in the year 1800 when transport and communication services were becoming faster and it was becoming more and more difficult to coordinate between locations which were too far away.
Then the concept of GMT was created in 1884. More than 26 countries were assembled in Washington D.C and it was decided that ‘Greenwich’ royal observatory will be treated as a point of origin for time.
We all know that all the places that are on the same longitude have the sun overhead at the same time. This time is called 12 pm or 12 noon. We have 24 hours of gap between 2 consecutive noons; this is the local time of the place.
The longitude that is marked on the map of India has been considered as the central longitude of India. This time is called IST (Indian Standard local Time) and it passes from the city of Allahabad in Uttar Pradesh.
Similarly, longitude lines that are 15o apart are considered as the local time of that place. There are 23 other time zones present other than GMT.
It is also essential to understand the difference between GMT and Local time as they are using interchangeably by many people.
GMT vs Local Time
The difference between GMT and Local time is that GMT (Greenwich Mean Time) is the reference time for all the other 23 time zones of the globe. Whereas, local time zones are the time at the longitudes on the globe surrounding prime meridian.
Comparison Table Between GMT and Local Time (in Tabular Form)
|Parameter of Comparison||GMT||Local Time|
|Implication||GMT (Greenwich mean time) can be treated as the middle most longitude line which is also called prime meridian.||The longitudinal lines on the globe are considered as the time reference of that place and are called the local time of that place.|
|Importance||Greenwich is located on the Prime Meridian, which decides the time lag for other countries.||It solves the problem of the time lag between different countries of the world.|
|Main features||Earth was divided into 24 different time zones. The countries on the right of Prime meridian are considered ahead in time and countries on the left were considered behind the time.||One day is the time passed between two peak positions of the sun. The longitudinal lines represent the local time.|
|History||GMT was created in 1884 when 26 different countries had a meeting on the topic of time lag. Greenwich royal observatory was considered as the point of reference.||As when GMT was created, local time was also created alongside. There are 23 more local time zones apart from GMT.|
|Advantages||We can easily tell the exact time in other countries with the help of GMT because it is located on the prime meridian.||Establishes the basis of time in different parts of the globe which are far away.|
What is GMT?
The full form of GMT is Greenwich Mean Time. Greenwich is a royal laboratory located in London which passes through the Prime Meridian of the globe.GMT is also called UTC (Universally coordinated time).
A total of 24 different time zones were created in 1884 in a meeting with 26 different countries in Washington D.C and all of the other 23 time zones (Local time zones) were referenced accordingly with the Prime meridian.
There is a difference of 15o in each successive time zones and farther the longitude is from the prime meridian, more the local time of that place is ahead or behind of the GMT.
The countries on the right of the prime meridian are ahead of GMT and the countries on the left of the prime meridian are behind GMT.
The creation of GMT also became advantageous as now we can easily tell the time in other countries with the knowledge of just GMT.
What is Local Time?
With the creation of GMT, the other 23 local time zones were also created. On the globe, there are a total of 24 different imaginary longitudinal lines which represent the basis of time in different parts of the world. In theory, one day is the time passed between two peak positions of the sun. The longitudinal lines represent the local time and the prime meridian represents GMT. India follows its local time which is known as IST (Indian Standard time).
Every longitude line is 15o apart from each other and for every 150, there is a time lag of two hours.
For example. If the time according to the Indian standard time zone is 6 pm, then in the UK the clock will be showing 12.30 p.m. And if the time according to IST is 9.30 pm, then it will be 3.30 pm in the UK as per the time guidelines of IST.
Farther the longitudinal line is from the prime meridian, more there will be a time gap between the GMT and that time zone.
Main Differences Between GMT and Local Time
- The main difference between GMT and local time is that GMT is a term that is usually used for places near London; whereas local time is the time zone at 23 different longitudinal lines.
- GMT is located at the prime meridian on the globe but on the other hand local time is determined by the time represented by the longitudinal lines present on the globe.
- GMT (Greenwich Mean Time) is considered as the base referral point for all other local time zones, whereas local time zones are calculated concerning the time represented by GMT.
- There is only one prime meridian therefore there is only one GMT over the globe, but 23 longitudinal lines are representing 23 different local time zones.
- Local times on the right of Prime Meridian are ahead of GMT and which are on left are behind the time of GMT.
One thing always creates confusion in our mind that what is meant by Daylight saving. And why some countries shift their time zone either forward or backward, and what is the reason behind it. Then GMT was created in the year 1884. More than 26 countries were assembled in Washington D.C and it was decided that ‘Greenwich’ royal observatory will be treated as a point of origin for time and other 23 longitudinal time zones were also created.