Why India Has a Half-Hour Time Zone
2026-02-02 · 8 min read
India uses Indian Standard Time (IST), fixed at UTC+5:30. It is one of the world’s most prominent half-hour offsets and applies nationwide without daylight saving time.
Why UTC+5:30 Was Chosen
After independence in 1947, India chose one national time to simplify railways, government operations, and communications. The offset was a compromise between historical local standards including Calcutta Time (UTC+5:53:28) and Bombay Time (UTC+4:51).
Why the Two-Zone Debate Persists
India spans nearly 30 degrees of longitude. In the far east, summer sunrise can come near 4:00 AM, while winter darkness can arrive close to 4:00 PM in parts of the northeast. That mismatch keeps debate alive about splitting India into two legal time zones.
Assam’s Tea-Garden Clock
Many tea estates in Assam use unofficial “Chaibagaan time,” typically one hour ahead of IST, to better match local daylight for field work.
Other Non-Hour Offsets
- Iran: UTC+3:30
- Afghanistan: UTC+4:30
- Myanmar: UTC+6:30
- Sri Lanka: UTC+5:30
- Nepal: UTC+5:45 (best-known national :45 offset)
See live clocks for Delhi, Mumbai, and Kolkata, or browse India.