Indian Standard Meridian and Indian Standard Time
Geography › Physical Geography of India · Topic 8.18
The Indian Standard Meridian is the 82.5° east longitude, which passes near Mirzapur in Uttar Pradesh and crosses five states: Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Odisha and Andhra Pradesh. Indian Standard Time (IST) is the local time of this meridian and is 5 hours 30 minutes ahead of Greenwich Mean Time (UTC). It is used throughout India, although the country extends about 29 degrees in longitude, from 68°7' E to 97°25' E, which makes a gap of nearly two hours in local solar time between Gujarat and Arunachal Pradesh.
5 min read · UPSC Prelims · Geography · Physical Geography of India
At a Glance
- Standard meridian 82°30′ E
- Near Mirzapur, Uttar Pradesh
- States crossed UP, MP, Chhattisgarh, Odisha, Andhra Pradesh
- IST UTC plus 5 hours 30 minutes
- East-west spread About 29 degrees, nearly 2 hours
- Exam link UPSC Prelims, Geography: Physical Geography of India
Where Does It Fit?
This topic closes the macro on the physical geography of India by returning to its location in longitude and time. It applies the general rules on time and longitude described in the first macro to the single time zone of the country. Previous topic: Coastal Plains, Coral Reefs and Islands of India (Andaman and Nicobar Islands, Lakshadweep). Next topic: Concept of Human Resources.
Why Is the Standard Meridian 82.5° East?
In short: 82.5° E lies near the middle of the country and is a multiple of 7.5°, so IST is a neat 5 hours 30 minutes ahead of Greenwich.
- Calculation: the Earth turns 15 degrees an hour, so 82.5 degrees means 82.5 divided by 15, or 5.5 hours ahead of the prime meridian, as in Local and Standard Time, International Date Line, Calendar.
- Location: the meridian passes near Mirzapur, close to Prayagraj, and crosses Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Odisha and Andhra Pradesh. It is roughly in the middle of the east-west extent of India, which is why it was picked.
- Extent of India: from about 68°7′ E in western Gujarat to 97°25′ E in Arunachal Pradesh, about 29 degrees, so the sun rises roughly two hours earlier in the north-east than in the west.
- Latitude: India’s extent in latitude is from 8°4′ N to 37°6′ N on the mainland, with the Tropic of Cancer (23.5° N) passing through eight states, which divides the country into nearly equal parts.
How Did IST Come About and Who Keeps It?
- History: before a common time, each city kept its own local time and the railways used Madras time. A standard time based on 82.5° E was adopted in 1906, though Calcutta and Bombay kept their own times for decades, until 1948 and 1955 respectively. Assam tea gardens continued with an informal ‘tea garden time’, an hour ahead of IST.
- Keeper of time: the CSIR-National Physical Laboratory in New Delhi maintains IST with atomic clocks and broadcasts it, with accuracy of a few nanoseconds.
- Legal status: India notified the Legal Metrology (Indian Standard Time) Rules in 2024, requiring the use of IST in official and commercial work. The details should be checked in the notification.
- Daylight saving: India does not use daylight saving time, since the country is mostly in the tropics where day length changes little through the year.
The general rules on local time, standard time and the date line are in Local and Standard Time, International Date Line, Calendar, and the grid of meridians in Latitude and Longitude – Important Parallels and Meridians.
Should India Have More Than One Time Zone?
| Case for | Case against |
|---|---|
| In the north-east the sun rises as early as 4 am in summer and sets by about 4 pm in winter, so daylight hours are lost | A single time is simple for railways, aviation, banking, broadcasting and administration |
| Better use of daylight could save electricity and improve productivity and school and work hours | Two zones may cause confusion, safety risks in railways and air traffic, and a divide between regions |
| Tea gardens already use their own time informally, and proposals for two zones, such as UTC plus 5:30 and UTC plus 6:30, have been studied by scientists | Gains could also be had by adjusting working hours in the north-east without a separate zone |
Governments have so far kept a single time zone, and proposals by experts, state governments and courts for a second zone for the north-east or a change in office hours have not been accepted. As an analytical point, the issue shows how a clock, which seems purely technical, links geography with national unity and daily life, and a longitude-based time fixes the same for all across a country of the width of India.
Why Is This Topic Important?
- Facts Meridian and offset are asked
- Debate Two time zones
- Link Longitude and time
What Came Next?
The next macro moves from the physical to the human geography, beginning with population and demography. Next topic: Concept of Human Resources.
Key People and Terms
- Standard meridian Reference longitude of a time zone
- IST Indian Standard Time
- UTC Coordinated Universal Time
- NPL National Physical Laboratory
- Daylight saving Shifting clocks to use summer light
- Tea garden time Informal Assam time, IST plus one hour
Exam Corner
Points to Remember
- Standard meridian: 82°30′ E.
- IST = UTC plus 5 hours 30 minutes.
- The meridian crosses five states.
- India spans about 29° of longitude.
- IST is kept by CSIR-NPL.
Do Not Confuse With
- Standard meridian and prime meridian 82.5° E versus 0° at Greenwich
- Tropic of Cancer and the standard meridian Parallel through eight states versus meridian through five
- IST and tea garden time Official versus informal Assam time
Memory Hook
Eighty-two and a half, five and a half from Greenwich; five states and a single clock.
Mains Angle
Questions ask for the case for and against more than one time zone. These points add depth.
- Basis Longitude and time
- Gap Two hours of daylight
- Decision Single time kept
A Question You May Face
An original practice question, not a past paper question.
“Why does India follow a single time zone and what are the arguments for and against introducing a second one?”
How to Answer
- Basis 82.5° E and IST.
- Gap Sunrise difference.
- Arguments For and against.
- Conclude Alternatives.
GS Relevance
Frequently Asked Questions
What is the Indian Standard Meridian?
The Indian Standard Meridian is the 82.5 degrees east longitude, from which Indian Standard Time is reckoned. It passes near Mirzapur in Uttar Pradesh and crosses Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Odisha and Andhra Pradesh. It lies near the middle of India's east-west extent.
Why is Indian Standard Time 5 hours 30 minutes ahead of GMT?
The Earth rotates 15 degrees of longitude in an hour, so the time at 82.5 degrees east is 82.5 divided by 15, or 5.5 hours, ahead of the prime meridian at Greenwich. That makes Indian Standard Time five hours and thirty minutes ahead of Greenwich Mean Time or Coordinated Universal Time.
Which institution maintains Indian Standard Time?
The CSIR-National Physical Laboratory in New Delhi maintains and disseminates Indian Standard Time, using atomic clocks to keep it accurate to within a few nanoseconds. The Legal Metrology (Indian Standard Time) Rules, notified in 2024, require the use of IST in official and commercial purposes.
Why is there a demand for a second time zone in India?
India spreads over about 29 degrees of longitude, so the sun rises nearly two hours earlier in the north-east than in Gujarat. Because the whole country follows one time, the north-east loses daylight in the evening, and so some argue for a separate zone or for different working hours.
Does India follow daylight saving time?
No. India does not use daylight saving time. The country lies mostly in the tropics, where day length changes little through the year, so there is little gain from shifting clocks. A single standard time is used throughout the year.
PYQ Practice — Statement Analysis
1 The Indian Standard Meridian passes through Mirzapur in Uttar Pradesh.
It is 82.5 degrees east.
2 Indian Standard Time is UTC plus 6 hours.
It is UTC plus 5 hours 30 minutes.
3 India follows daylight saving time in summer.
It uses a single time all year.
4 The standard meridian of India passes through Arunachal Pradesh.
It passes through UP, MP, Chhattisgarh, Odisha and Andhra Pradesh.
Past Mains Questions on This Topic
This topic comes under Physical Geography of India. UPSC Mains questions asked on the matching syllabus topic, year-wise with marks:
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