Q1.
Return to the two friends sitting in Gujarat and Assam. Use this example to explain the difference between local time and standard time.
Answer
The two friends give us both kinds of time at the same moment.
| Local time | Standard time | |
|---|---|---|
| What decides it | The Sun over that particular meridian — it is 12 noon when the Sun is highest there | One meridian chosen for the whole country |
| In our example | The Sun has already set at Tinsukia (95°E) while it is still day at Porbandar (70°E) — their local times differ by about 1 h 43 min | Both friends' clocks and phones show exactly the same time, because both follow IST |
| How many in India | A different one for every meridian — thousands of them | Only one: IST = GMT + 5:30, based on 82°30′E, which passes near Mirzapur in Uttar Pradesh |
| Why we need it | It matches daily life with the Sun | It lets trains, flights, schools, offices and TV news work to one timetable |
Putting it in one sentence: local time is the time the Sun shows you where you stand; standard time is the time the country agrees to keep on its clocks.
Why a country must choose: if every town kept its own local time, a train leaving Ahmedabad at 10 am would reach Guwahati at a time no timetable could state. So India fixed one meridian — 82°30′E — and every clock from Kutch to Kibithu follows it, even though the Sun does not.
Did you know? Before 1906 India had several local times, including separate Bombay Time and Calcutta Time, which differed by about 40 minutes. Bombay Time was used in the city until 1955.