Difference Between IST and GMT – GMT vs IST

Difference Between IST and GMT

UT1 is the modern form of mean solar time at 0 degrees longitude. UTC and UT1 differ by up to 0.9 seconds. A time zone of a certain region of the world observes a standardized time for retail, social, and lawful objectives. GMT and IST are two such time zones. The difference between GMT vs IST is discussed below in a tabular form.

GMT vs IST

Difference Between IST and GMT
Basis of Difference	Indian Standard Time (IST)	Greenwich Mean Time (GMT)
History	IST was established in India in 1947 after India gained independence from British Rule.	GMT was established in 1675 by the Royal Observatory to help navigators at sea.
Time Calculation	The Clock tower in Mirzapur is the basis of the calculation of IST. The tower coordinates are- 25.15 degrees North Latitude and 82.58 degrees East longitude.	GMT is considered equivalent to UTC (Universal Coordinated Time) for UK Civil purposes but is deemed equal to UT1 for navigation.
Accuracy	The Time and Frequency Standards Laboratory at the National Physical Laboratory in New Delhi generates the official time signal for IST. The signals are based on atomic clocks that are synchronized with UTC.	GMT calculates time-based on Sun. However, because of the earth’s uneven angular velocity and tilt in its axis, noon GMT may not be the exact time when the sun reaches the highest point in the sky.
Replacement and Sufficiency	Demand for separating India into different time zones has been raised repeatedly. A time zone differentiated by one hour has been requested for Northeastern regions.	UTC replaced GMT as the international time standard in 1972. UTC is based on atomic measurements and hence is more accurate.
Countries that follow the time zone	IST is used in India and Sri Lanka.	GMT is used in the UK and other commonwealth nations such as Australia, New Zealand, and the countries of the Eastern Hemisphere.

IST and GMT

The difference between IST and GMT is based on various factors, which include full form, history, countries which follow that particular time zone, how both the time are calculated, etc. IST was established in 1947, and GMT was established in 1675.

What is IST?

The IST Full Form is Indian Standard Tim. It is used in India and Sri Lanka and was established in 1947 after India gained its independence. The IST is calculated from a clock tower in Mirzapur with directions 25.15 degrees North Latitude and 82.58 degrees East Longitude.

However, Kolkata and Mumbai adopted it only in 1948 and 1955, respectively.

What is GMT?

GMT stands for Greenwich Mean Time and was established in 1675. The Royal Observatory built it to assist the mariners in determining longitude at sea. It also helped them keep a standard reference time concerning other cities of England that used to keep different local times.

• The Shepherd Gate Clock displays GMT Time at the Royal Observatory in Greenwich, London.
• When the sun is at its highest point above the Prime Meridian, it is noon at Greenwich.
• It is the reference point for every time zone in the world. Some GMT countries include the UK, Iceland, Greenland, and Ghana.
• GMT Time or Greenwich Mean Time in India is measured on Earth’s 0-degree longitude, which passes through Old Royal Observatory near London.
• India is +5:30 hours ahead of the GMT time.
• The GMT is now known as the Universal Coordinated Time (UTC).

Conclusion:

Key Difference Between IST and GMT

The key Difference Between IST and GMT is that IST is Indian Standard Time which is the time zone observed throughout India, GMT is Greenwich Mean Time (GMT), which is the mean solar time at the Royal Observatory in Greenwich, London.

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