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Time Zone Calculator

Pick a moment in one zone, read it in another — daylight saving handled automatically, day changes flagged, and the offset gap spelled out.

Convert a moment all IANA zones · DST-aware

Converted time
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Offset difference
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§1How conversion works

wall time + zone → one absolute instant (UTC) → wall time in the other zone IST = UTC +5:30, fixed all year (India has no DST)

Zones aren't just hour offsets — half-hour (India, Sri Lanka) and even 45-minute (Nepal, Chatham Is.) offsets exist, and many countries shift twice a year for daylight saving. The only safe path is through the absolute instant, which is what this page (and every OS) does.

Worked example — a 9:00 PM IST client call with New York
21:00 IST = 15:30 UTC (IST = UTC+5:30) July → New York is on EDT (UTC−4) → 11:30 AM, same day January → New York is on EST (UTC−5) → 10:30 AM, same day same meeting, one hour of drift across the year — India never moved.

§2The gotchas

“EST” is ambiguous — cities aren't

New York is EST in winter but EDT in summer; the IST↔New York gap swings between 10:30 and 9:30 across the year. That's why the picker uses city zones (America/New_York) — the abbreviation alone can't tell you which offset applies on a given date.

Meetings across the date line

A 9 PM IST call is already tomorrow in Sydney and still this morning in San Francisco. The day-shift flag above (−1d/+1d) is the difference between joining a meeting and missing it by 24 hours.

§3Related

Duration between two moments, date arithmetic.