What is India Standard Time? Do people in Assam and Gujarat have a disadvantage because of IST?

In one line

The rule

India Standard Time (IST) is the time observed throughout India, set at 5 hours and 30 minutes ahead of Coordinated Universal Time (UTC+5:30).

Let's understand it simply

Imagine you and your friend both use the same clock, but you live in Assam (far east) and your friend lives in Gujarat (far west). The Sun rises and sets much earlier in Assam than in Gujarat, but both of you follow the same clock time. This is because India uses only one time zone for the whole country—IST. The clock is set according to a line of longitude (82.5° East) that passes near Allahabad (Prayagraj), which is roughly in the middle of India. So, for people in the east, the day starts and ends earlier by the Sun, and for people in the west, it starts and ends later.

How it works

1. The Earth is divided into 24 time zones, each about 15° of longitude apart.
2. India stretches almost 30° from east to west, but uses only one time zone: IST (UTC+5:30).
3. IST is based on the 82.5°E longitude, near Allahabad (Prayagraj).
4. In Assam (about 92°E), the Sun rises and sets earlier than IST clock time.
5. In Gujarat (about 68°E), the Sun rises and sets later than IST clock time.

The story behind it

India adopted IST in 1906, during British rule, to have a single standard time for the whole country. Before that, different cities had their own local times. The 82.5°E longitude was chosen because it is roughly in the middle of India. Some regions, like Assam, once used their own local time (called "Chaibagaan time") for tea gardens, but now everyone follows IST.

Where you see it in real life

• School timings in Assam: Schools may start classes when it is still dark, because the Sun rises early but the clock shows a later time.
• Shops in Gujarat: Shops may stay open late because the Sun sets late by the clock, so people finish work later.
• TV shows: National TV programs air at the same time everywhere, but in Assam, it may feel too early or too late compared to local daylight.
• Train schedules: All trains run on IST, so people in the east and west have to adjust their daily routines.

Why it matters

• Daily routine: People in Assam may have to wake up before sunrise for school or work, while in Gujarat, people may work until after sunset.
• Energy use: More electricity is used for lights in the morning in Assam and in the evening in Gujarat, because the clock does not match the Sun.
• Productivity: Some people feel tired or less productive because their body clock (circadian rhythm) does not match IST.
• Debate on time zones: There are discussions about whether India should have two time zones to solve these problems.

Common mistakes

• Thinking IST is the same as the local time everywhere in India. It is not—sunrise and sunset times are very different in Assam and Gujarat.
• Believing that having one time zone is always best. It is convenient, but it causes problems for people far from the central longitude.

Remember it

India uses one time for all—IST (UTC+5:30)—but this means the Sun rises and sets at very different clock times in the east and west.