Unix timestamp converter
Convert exact Unix seconds or milliseconds to UTC and back with a live instant preview.
How it works & useful details
How it works & limits
Unix time counts from 1970-01-01 00:00:00 UTC. Seconds support up to three fractional digits; milliseconds must be integers. Choose the unit explicitly, including for negative timestamps.
UTC input must use YYYY-MM-DDTHH:mm:ss[.SSS]Z. Years 0001–9999 are supported. Leap seconds and sub-millisecond precision are not represented. No local timezone is inferred.
Your working space
Explore the live preview, then save a copyable text report. Inputs stay on this device and are cleared by refreshing. Dates use the Gregorian calendar, including before its historical introduction.
About this tool
Unix timestamp converter turns Unix seconds or milliseconds into a UTC date and back again, with a live preview of the instant. It is the quickest way to check a timestamp from a log, an API response, or a database row.
Both directions are supported, and the tool shows UTC explicitly so there is no ambiguity about whose local time is displayed. Conversions happen locally in the page.
How to use it
- Choose the direction: timestamp to date, or date to timestamp.
- Enter the value and select seconds or milliseconds.
- Read the UTC representation and the equivalent timestamp.
- Copy the result you need for a log, query, or issue.
Worked examples
- 0 seconds = 1970-01-01T00:00:00.000Z, the Unix epoch.
- 1790001774 seconds = 2026-09-21T14:42:54.000Z.
- 1790001774000 milliseconds is the same instant. JavaScript's Date.now() and many JSON APIs use milliseconds, while Unix tools, databases, and JWT exp/iat claims use seconds.
A quick way to tell them apart: current timestamps in seconds have 10 digits, and in milliseconds 13 digits. The tool asks you to choose the unit explicitly, because guessing goes wrong for dates close to 1970 and for negative values.
Things to know about Unix time
Unix time counts seconds since the epoch in UTC and ignores leap seconds, so every day is exactly 86,400 seconds. It has no time zone. The same timestamp is the same instant everywhere, which is why it is a good format for storage and logs.
Systems that store the value as a signed 32-bit integer overflow at 2038-01-19T03:14:07Z, the "Year 2038 problem". Negative timestamps represent dates before 1970. For example, −86400 seconds is 1969-12-31.
Frequently asked questions
How do I tell whether a value is seconds or milliseconds?
Seconds timestamps are around ten digits today, milliseconds around thirteen. If the resulting date looks far off, switch the unit.
Does it use my local time zone?
Results are shown in UTC. Use the Timezone converter to see the same instant in local zones.
What range of timestamps is supported?
Values within the range of JavaScript dates, which covers ordinary log and application timestamps.