Date & Time
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Unix Timestamp Converter — Epoch, ISO & Time Zones
Convert Unix seconds and milliseconds to UTC, local, and IANA zones. ISO-8601, RFC 2822, relative time, and batch convert — privately in your browser.
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Version 1.0.0 · Last reviewed
How it worksShow guide
Introduction
Unix time counts seconds (or milliseconds) since 1970-01-01 00:00:00 UTC. This converter auto-detects 10-digit seconds vs 13-digit milliseconds, formats the instant in UTC and a chosen IANA zone, and can batch-convert one value per line. Nothing is sent to a server.
Step-by-step
- Paste a Unix timestamp or ISO-8601 string — or pick a date
- Choose an IANA time zone
- Copy seconds, milliseconds, ISO, or RFC 2822
Worked example
1577836800 seconds is 2020-01-01 00:00:00 UTC. In Asia/Kolkata that instant is 05:30 the same morning.
Use cases
- Decode log timestamps from APIs and databases
- Build ISO-8601 strings for a specific time zone
- Convert a spreadsheet column of epoch values in one paste
Frequently asked questions
Seconds or milliseconds?
Values around 10 digits are treated as seconds; around 13 digits as milliseconds. Mixed units are the usual source of “47 years off” bugs.
Is Unix time timezone-aware?
The epoch itself is UTC. Displaying it in New York or Kolkata is a formatting choice — the underlying instant does not change.
Does this handle leap seconds?
JavaScript Date ignores leap seconds, like most application clocks. Do not use this for legal UTC-SLS or astronomical work.
Why can DST dates look wrong?
Converting a local civil time into an instant near a daylight-saving fold can be ambiguous. Prefer UTC or ISO strings with an offset when precision matters.
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