Question

Indian standard time (IST) refers to the local time of which city?

Answer 1

Hint: The synchronization of clocks within a geographic region to a single time standard, rather than a local mean time standard, is known as standard time. Standard time generally agrees with local mean time at some meridian that passes through the region, usually near the center.

Complete answer:
- Indian Standard Time is abbreviated as IST.
- The Union government established IST as the official time for the entire country after Independence in 1947, though Kolkata and Mumbai kept their own local time (known as Calcutta Time and Bombay Time, respectively) until 1948 and 1955. The Central Observatory was relocated from Chennai to Shankargarh Fort in the Prayagraj district to be as close to UTC+05:30 as possible.
- The Prime Meridian is the longitude meridian that passes through the Greenwich Observatory, according to an international agreement (near London).
- Prime Meridian has been given the value of 0°.
- Indian Standard Time is 5 hours and 30 minutes ahead of Greenwich Mean Time.
- According to popular belief, the standard meridian was chosen in multiples of 7°30′ longitude.
- The ‘standard meridian' of India is chosen to be 82°30′ E.
- The sun travels 15 degrees of longitude per hour, or one degree of longitude, every four minutes.
- Due to their vast west-to-east extent, some countries, such as the United States and Russia, have more than one standard meridian.

What purpose does the standard Meridian serve?
- The Standard Meridian is the time at the country's central meridian, and its local time is used as the country's standard time.
- This is done to the greatest extent possible to maintain time uniformity within a country's territorial limits.
- As we travel from Gujarat to Arunachal Pradesh, there is a two-hour time difference.
- As a result, the time along the Standard Meridian of India (82°30'E), which passes through Mirzapur, is the standard time for the entire country. Mirzapur is a town in the state of Uttar Pradesh.
- We use the rate at which the sun traverses over certain degrees of longitudes to determine the local time of an area in relation to the time at the Prime Meridian (0°Longitude).
- The clock tower in Mirzapur near Allahabad, Uttar Pradesh, is approximately on the corresponding longitude reference line, and Indian Standard Time is calculated on the basis of 82.5 degrees east longitude.

Thus, Indian standard time (IST) refers to the local time of Mirzapur near Allahabad.

Note: As it passes through almost the entire country of India, IST is used as the standard time. The precise time is broadcast on the national All India Radio and Doordarshan television networks to inform the public. Telephone companies have dedicated phone numbers that are linked to mirror time servers, which also relay the exact time. Another increasingly popular method of obtaining the time is through Global Positioning System (GPS) receivers.