How this calculator works
- Step 1Count from the epoch1 Jan 1970 UTCA Unix timestamp is the number of seconds since then.
- Step 2Split into days86,400 s a dayWhole days become a calendar date; the rest is the time.
- Step 3Shift for the zone+05:30 for ISTThe same instant shown in India time and in UTC.
A timestamp names one instant, the same everywhere in the world. Only the way you write it as a date depends on the time zone.
Worked example: 1,700,000,000 seconds
1700000000 is Tue, 14 Nov 2023, 22:13:20 UTC, which is Wed, 15 Nov 2023, 03:43:20 IST in India.
- Days and seconds
1700000000 ÷ 86,400 = 19675 days + 80000 seconds
- Whole days after 1 Jan 197019675
- Seconds into that day80000
- UTC2023-11-14T22:13:20Z
- Add 5 hours 30 minutes2023-11-15T03:43:20+05:30
- In IndiaWed, 15 Nov 2023, 03:43:20 IST
Going the other way, 2026-10-27 09:30 in IST is the timestamp 1793073600.
Reading the result
- Seconds (10 digits today)1700000000Used by Unix, most databases, JWTs and many APIs.
- Milliseconds (13 digits today)1700000000000Used by JavaScript’s Date.now() and many front ends.
- ISO 8601The standard for APIs and logs, with Z or +05:30.
- RFC 2822The format used in email headers.
- RelativeHow long ago, or how long from now.
- Your deviceThe time in your own device’s zone.
Related time tools
A Unix timestamp counts seconds since 1 January 1970 in UTC.
To convert a time between zones, use the time zone converter. The cron expression explainer shows a schedule’s next runs, and the JWT decoder reads timestamps inside tokens.
Common mistakes
Mistake: Treating milliseconds as seconds.
Instead: Check the digit count: 13 digits today means milliseconds.
Mistake: Storing local India time without an offset.
Instead: Store UTC or add +05:30 so the instant is unambiguous.
Mistake: Keeping 32-bit timestamps in long-lived systems.
Instead: Signed 32-bit seconds run out on 19 January 2038; use 64-bit.
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