Scheduling with India: What UTC+5:30 Means for Your Calendar
India Standard Time (IST) is UTC+5:30. The half-hour trips people up. Most calendar tools and most people doing mental arithmetic assume hourly offsets. When the gap is 5:30, the result never falls on a round number: a 9am New York call lands at 7:30pm IST, not 7pm or 8pm. A 3pm London call lands at 8:30pm IST. The half-hour consistently pushes calls later into the Indian evening than expected.
IST doesn’t shift — but your time zone does
India doesn’t observe daylight saving time. The offset is always UTC+5:30. When the US or Europe moves clocks forward or back, IST stays fixed — which means the gap between your city and India changes by 30 minutes (not a full hour) twice a year. A recurring India call that you set up in winter will be 30 minutes off after your DST transition. Worth checking.
Overlap windows
IST business hours: typically 9am–6pm (03:30–12:30 UTC)
| Your location | Usable overlap with IST (9am–6pm) |
|---|---|
| London (GMT) | 9am–12:30pm GMT — tight but workable |
| London (BST) | 9am–12:30pm BST — slightly better |
| New York (EST) | 9am EST = 7:30pm IST — no standard overlap |
| New York (EDT) | 9am EDT = 6:30pm IST — barely overlaps end of day |
| San Francisco (PST) | 9am PST = 10:30pm IST — no overlap |
| Singapore (SGT) | Mornings in Singapore line up well |
For US teams, India is effectively async-first. The only synchronous options are early morning IST (which lands as the previous late evening in the US) or late evening IST (which lands as early morning US). Neither is sustainable as a regular recurring slot — but early morning IST at 7:30–9am, landing as East Coast late afternoon, is the least painful recurring option.
For Europe–India calls, the London morning window (before 12:30pm GMT) lands in the Indian afternoon. That’s the cleanest overlap with nobody outside normal hours.
Use meetwhen with Asia/Kolkata — it handles the 30-minute offset correctly and shows the exact overlap window.
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