How to use
- Choose Auto detect, Unix seconds, Unix milliseconds, or ISO 8601 / date-time as the input type.
- Paste the value. If a local date-time has no Z or offset, confirm the visible source IANA time zone.
- Search for an IANA time-zone ID or city and select the zone used for the readable output.
- Compare UTC, the selected-zone offset, seconds, and milliseconds, then copy one field or all results as JSON.
Examples
- Input
1710000000- Output
2024-03-09T16:00:00.000Z
A 10-digit Unix value is normally seconds.
- Input
1710000000000- Output
2024-03-09T16:00:00.000Z
A 13-digit Unix value is normally milliseconds.
- Input
2024-03-10T00:00:00+08:00- Output
2024-03-09T16:00:00.000Z
The +08:00 offset and UTC Z value describe the same instant.
- Input
2024-03-09T16:00:00Z- Output
2024-03-10 00:00:00 Asia/Taipei
Z is UTC; selecting Asia/Taipei changes only the displayed clock time.
- Input
2024-03-10T02:30:00 in America/New_York- Output
Rejected as a nonexistent local time
The clock jumps from 01:59 to 03:00 during this daylight-saving transition.
Understanding the result
A Unix timestamp is an instant count and contains no time-zone field. Unix seconds count whole seconds since 1970-01-01T00:00:00Z; milliseconds use the same epoch with three additional digits of precision.
ISO 8601 is a date-time representation. Z means UTC; an offset such as +08:00 states how the written clock time relates to UTC.
A local date-time is a display of an instant in a selected IANA time zone. The browser applies the historical or daylight-saving offset for that date; changing the display zone does not change the instant.
Common errors and limitations
- An invalid calendar date, unsupported text, or a number outside the JavaScript Date range cannot be converted.
- Digit count is a useful seconds-versus-milliseconds hint, not a universal guarantee. Select the input unit explicitly when the source format is known.
- A date-time without Z or an offset may be interpreted in the browser's local time zone, which can differ between devices.
- Historical and daylight-saving displays depend on the IANA time-zone data available in the browser. A skipped local time is rejected; a repeated time requires choosing the earlier or later offset.
Frequently asked questions
- What is a Unix timestamp?
- It is a numeric count from the Unix epoch at 1970-01-01T00:00:00Z. Systems commonly store the count in seconds or milliseconds.
- Is my timestamp in seconds or milliseconds?
- Current Unix seconds are usually 10 digits and current milliseconds are usually 13 digits. Use the source API or schema as the authority instead of relying only on length.
- What does Z mean in ISO 8601?
- Z is the UTC designator, equivalent to an offset of +00:00.
- Does converting a timestamp change the moment in time?
- No. A correct conversion changes the representation or display time zone while preserving the same instant.
- How does the converter handle daylight-saving time?
- It uses the browser's IANA time-zone data for the date being converted. Nonexistent clock times are rejected, and repeated clock times require an earlier-or-later offset choice.