Unix Timestamp & Time Zone Converter
Convert Unix seconds, Unix milliseconds, and ISO 8601 dates into UTC, your local time, and any IANA time zone. Daylight-saving rules come from the browser’s time-zone database, not hardcoded offsets.
All processing happens locally in your browser. Your input is never uploaded.
Accepts Unix seconds, Unix milliseconds (auto-detected by size), and ISO 8601 dates. Negative Unix values reach before 1970.
The full browser time-zone list loads with JavaScript.
- UTC
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- Local time
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- Selected time zone
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- ISO 8601 (UTC)
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- Unix seconds
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- Unix milliseconds
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- Relative time
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How this timestamp converter works
Unix seconds versus milliseconds
Unix time counts from 1970-01-01T00:00:00 UTC. APIs and databases commonly store it as seconds (ten digits for current dates) while JavaScript and many logging systems use milliseconds (thirteen digits). Auto-detection treats magnitudes below 100,000,000,000 as seconds and larger values as milliseconds; the unit override wins whenever a value is ambiguous. Negative values are valid and reach before 1970.
UTC versus local time
A Unix timestamp names one exact instant; time zones only change how that instant is written. The converter shows the instant in UTC, in the time zone your browser reports, and in any IANA zone you select (for example Asia/Singapore or America/New_York), always with the UTC offset in effect at that moment.
ISO 8601 input
ISO 8601 strings such as 2026-07-29T14:30:00Z are the least ambiguous input. A trailing Z or an explicit offset like +08:00 pins the instant exactly. A date-only value such as 2026-07-29 means midnight UTC. A date-time without any offset is read in your device's local time zone, and the tool says so — prefer an explicit offset when precision matters.
Daylight-saving handling
Conversions use the IANA time-zone database built into your browser through the Intl API. Offsets therefore follow real daylight-saving rules — America/New_York switches between GMT-05:00 and GMT-04:00 on the correct dates — rather than a fixed "add N hours" shortcut, including for historical dates.
Privacy
Detection, parsing, and every conversion run in your browser. Nothing you enter is uploaded, logged, or stored by winterm.dev. See the privacy policy for the website-wide details.