Unix Timestamp / Timezone Converter
Formats, precision, range and timezone rules
Unix epoch is 1970-01-01T00:00:00Z. Choose units explicitly: seconds allow a dot and up to three fractional digits; milliseconds are whole integers. Negative values are supported. Group separators, exponent notation and sub-millisecond values are rejected. Output seconds retain the exact millisecond fraction (for example -0.001), not rounded whole seconds.
ISO input is yyyy-MM-ddTHH:mm:ss with optional .f, .ff or .fff, followed by optional Z or ±HH:mm (maximum ±14:00). Explicit offsets define the instant independently of the selected zone. Without an offset, the selected zone interprets the local time. DST gaps are rejected; overlaps require an explicit offset and never silently choose one. Leap seconds and date-only input are not supported.
Supported UTC range: 0001-01-01T00:00:00.000Z through 9999-12-31T23:59:59.999Z. Selected-zone display must also fit years 0001–9999; out-of-range conversion is rejected, not clamped. Output always shows three millisecond digits and a UTC Z or numeric offset. Timezone rules use the same embedded TZDB: 2026f (mapping: 49) data on server and WebAssembly, independent of OS/ICU updates. Historical numeric offsets retain seconds when necessary (for example -00:44:30); use the UTC result or epoch value for reverse conversion when an offset contains seconds.
The selector uses the IANA 2026f identifier catalog, with UTC, regional zones, fixed offsets and explicitly labelled aliases. Each identifier appears once and the exact selected ID is retained. Missing legacy links resolve through their versioned IANA target; conversion rules come from pinned embedded TZDB data rather than host timezone data. Search is case-insensitive and spaces match underscores. The selected timezone stays available outside the filter; unavailable zones produce an error, never a UTC fallback.
Retained selector exclusions: CST6CDT, EST5EDT, MST7MDT, PST8PDT are legacy POSIX-rule IDs excluded from the original qualified selector and are still not offered. They are not guessed as regional zones. For Etc/GMT fixed offsets the IANA sign is reversed (Etc/GMT+5 means UTC-05:00). Regional zones use historical/DST rules, not a fixed present-day offset.
No clock, external conversion API or automatic input storage is used. The website uses Interactive Auto: server-interactive input traverses the Blazor connection; WebAssembly executes on your device. This tool is currently enabled on Web only; extension and Android are not qualified.
Unix Timestamp / Timezone Converter guide
Convert Unix timestamps and ISO-8601 dates in either direction.
Input and limitations
Explicit seconds or milliseconds, or ISO-8601 with an optional offset. Offset-free dates use the selected timezone.
Check the selected options before using the result. Formatting and conversion do not establish that data is safe or suitable for your application.
How to use Unix Timestamp / Timezone Converter
- Choose the input format and timezone, then enter a value.
- Choose Convert to see Unix seconds, milliseconds, UTC and selected-zone ISO-8601.
- For a DST overlap, supply one of the offsets shown in the error; nonexistent local times are rejected.
- Clear removes the input, result and error; input format and timezone stay selected.
Example
With Unix seconds and UTC selected, 0 converts to 1970-01-01T00:00:00.000Z. Switch to ISO-8601 and enter 1970-01-01T02:00:00+02:00 to get the same epoch. -0.001 seconds equals -1 millisecond.
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