What is a Unix timestamp?

A Unix timestamp is the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970, known as the Unix epoch. It is a timezone-independent way to represent an instant in time, widely used in programming and databases.

How does it know seconds versus milliseconds?

The tool checks the magnitude of the number. Values with 13 or more digits (roughly a trillion or more) are treated as milliseconds, while shorter values are treated as seconds. Current-era second timestamps have 10 digits and millisecond timestamps have 13.

ISO 8601 is the international standard date format, for example 2026-06-06T14:30:00.000Z. The trailing Z means the time is in UTC. It sorts correctly as text and is unambiguous across locales.

How are timezones handled?

The formatted output uses the browser's built-in Intl API with the IANA timezone you select, so it applies the correct UTC offset and daylight saving rules for that zone on that date.

Is any data sent to a server?

No. All parsing and formatting happens locally in your browser using the standard JavaScript Date and Intl APIs. Nothing is transmitted.

Unix Timestamp Converter

A Unix timestamp counts the seconds since the Unix epoch — midnight UTC on 1 January 1970. It is the most common way programs store a moment in time because it is a single number with no timezone attached. This free converter turns that number into a readable date in any timezone, and turns dates back into epoch values.

How it works

When you paste a timestamp, the tool first decides whether it is in seconds or milliseconds. It does this by magnitude: a value of 13 or more digits is treated as milliseconds (the unit JavaScript’s Date uses internally), and a shorter value is treated as seconds and multiplied by 1000.

It then builds a JavaScript Date from those milliseconds and formats it two ways:

ISO 8601 in UTC, e.g. 2026-06-06T14:30:00.000Z, produced by toISOString().
A locale-formatted string in your chosen IANA timezone, produced by the Intl.DateTimeFormat API, which applies the correct UTC offset and daylight-saving rules for that zone and date.

The reverse field takes a date and time and returns the matching epoch in both seconds and milliseconds.

Tips and notes

A live clock at the top shows the current Unix time so you can grab “now” instantly.
If you are unsure of a value’s unit, paste it and read the Interpreted as row — it tells you whether it was read as seconds or milliseconds.
Timestamps are UTC by definition; the timezone selector only changes how the same instant is displayed, never the underlying value.
Everything is computed locally with the browser’s standard date APIs, so it is safe to use with internal or sensitive timestamps.