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Unix Timestamp Converter

Convert Unix timestamps in seconds or milliseconds to UTC dates, and timezone-stamped ISO dates back.

Paste the integer timestamp, select seconds or milliseconds, then convert. To go the other way, enter an ISO date and time with Z or an explicit offset such as +08:00.

Enable JavaScript to convert timestamps locally in your browser.

Timestamp to UTC date

Select the unit used by your Unix timestamp.

Timezone date to timestamp

Include Z or a UTC offset so the instant is unambiguous.

Example: 2026-09-25T08:30:00+08:00

How to use

Convert a log timestamp to a UTC date

Convert Unix timestamps in seconds or milliseconds to UTC dates, and timezone-stamped ISO dates back.

Step by step

  1. Provide the source using: Unix timestamp / ISO 8601 date and time.
  2. Set: Timestamp unit. Use the reference below to choose the options that fit your task.
  3. Choose: Convert to UTC / Convert to Unix timestamp. Inspect the result before copying, downloading or using it elsewhere.
  4. Paste the integer timestamp, select seconds or milliseconds, then convert. To go the other way, enter an ISO date and time with Z or an explicit offset such as +08:00.

Choosing the settings

OptionWhat changes
Timestamp unitUnix timestamps count time from 1970-01-01 UTC. Seconds and milliseconds differ by a factor of 1,000; choose the unit explicitly. Results include a UTC ISO date and both timestamp units.
ISO 8601 date and timeA local clock time can refer to different instants in different timezones. Enter an ISO 8601 date and time ending in Z or an explicit offset such as +08:00. This tool does not guess your device timezone or handle leap seconds.

Example and expected result

1700000000 seconds is 2023-11-14T22:13:20.000Z. The ISO value 2023-11-15T06:13:20+08:00 converts back to 1700000000 seconds and 1700000000000 milliseconds. A local date without a timezone is rejected rather than guessed.

If it is not working

  • If the converted year is far from what you expect, check seconds versus milliseconds before changing the number. For a rejected date, add the correct Z or explicit offset from the source record; do not invent a timezone.

How timestamp units work

Unix timestamps count time from 1970-01-01 UTC. Seconds and milliseconds differ by a factor of 1,000; choose the unit explicitly. Results include a UTC ISO date and both timestamp units.

Why must the date include a timezone?

A local clock time can refer to different instants in different timezones. Enter an ISO 8601 date and time ending in Z or an explicit offset such as +08:00. This tool does not guess your device timezone or handle leap seconds.

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