Question

Briefly describe the problems of using local time. What is the difference between the International Meridian (GMT) and the Standard Meridian of India (IST)?

Answer 1

Instruction:

Explain the challenges of adopting local time. Detail upon GST, IST and how they are calculated.
Answer:

Local time is calculated with reference to the prime meridian at 0O .
The difference between the local time of any two consecutive longitudes is 4 minutes.
Adopting local time leads to challenges, such as

• Preparation of timetables for trains crossing several longitudes.
• Synchronising flight timings across the country
• Synchronising office timings across the country. Therefore, it is essential to adopt the local time of one central meridian of a country as the standard time for the whole country.

Standard time is the fixed time for places falling in the same meridian, set in a country by law.
There are a total of 24 time zones. Globally, the local time in Greenwich (Greenwich Mean Time) in England is considered the international standard time.
India has a vast longitudinal extent. It has many local times passing through it. In India, 82 ½ °E longitude determines the standard time. Thus the standard Meridian of India is 82°30’E

• Mirzapur’s distance from Greenwich = 82.5°E
• Time difference = 82.5 × 4 = 330 mins = 5 hours 30 min
• IST = GMT + 5:30

The Indian Standard Time is 5 hours 30 minutes ahead of GMT.