Unix Timestamp Converter
Convert epoch timestamps to human-readable dates and back. Seconds and milliseconds are detected automatically, and results are shown in UTC, your local timezone, and ISO 8601.
No date chosen
Pick a date and time above to convert it into Unix seconds, milliseconds, and an ISO 8601 string.
How to Use
- To decode a timestamp, paste it into the first field. You do not need to say whether it is in seconds or milliseconds — the tool works it out from the magnitude and tells you which it assumed.
- Read the UTC, local, and ISO 8601 renderings, plus a plain-English relative time such as "3 days ago".
- To encode a date, use the date-and-time picker in the second section. The value you choose is interpreted in your device's local timezone.
- Use the copy button beside any row to put that value on your clipboard.
Features
- Automatic detection of seconds versus milliseconds, with the assumption shown
- Live current-timestamp readout that ticks every second, with one-click copy
- UTC, local, ISO 8601, seconds, milliseconds, and relative time in one view
- Bidirectional — decode a timestamp or encode a picked date
- Handles negative timestamps for dates before the 1970 epoch
What a Unix Timestamp Is and Why Everything Uses One
A Unix timestamp, also called epoch time or POSIX time, counts the seconds elapsed since midnight UTC on 1 January 1970. That single integer is the closest thing computing has to an unambiguous description of a moment. A string like "03/04/2026 8:00" raises three immediate questions — is that March or April, is it morning or evening, and in which timezone? A timestamp raises none of them, which is why databases, log files, JSON APIs, JWT expiry claims, and file metadata all lean on it so heavily.
The confusion in practice is units. The Unix convention is seconds, but JavaScript's Date.now() returns milliseconds, and plenty of systems mix the two. The tell is the length: a present-day timestamp in seconds is ten digits, while the same instant in milliseconds is thirteen. This converter uses that magnitude — anything at or beyond one trillion is treated as milliseconds — and states its assumption on screen so you can catch a misread instantly. If you ever see a date in 1970 where you expected today, you have almost certainly fed milliseconds into something expecting seconds; divide by a thousand. The mirror-image bug lands you tens of thousands of years in the future.
Two further wrinkles are worth knowing. Unix time deliberately ignores leap seconds — every day is exactly 86,400 seconds long by definition — which keeps arithmetic simple at the cost of drifting a handful of seconds from strict astronomical time. And systems that store the value in a signed 32-bit integer overflow on 19 January 2038, the so-called Year 2038 problem, which is why modern platforms have moved to 64-bit representations. Negative timestamps are perfectly legal too: they describe instants before 1970, and this tool decodes them correctly.
Frequently Asked Questions
How does the tool know if my number is seconds or milliseconds?
By magnitude. Values with an absolute size of one trillion or more are treated as milliseconds, everything smaller as seconds. The detected unit is displayed above the results so you can see exactly what was assumed.
Why is the local time different from the UTC time?
They are the same instant expressed in two different frames. UTC is the global reference; the local row applies your device's timezone offset, including daylight saving if it was in effect on that date.
Can I convert dates before 1970?
Yes. Timestamps before the epoch are negative, and the converter handles them. Enter −86400, for example, and you get 31 December 1969.
What timezone does the date picker use?
Your device's local timezone. The wall-clock time you choose is converted to the corresponding UTC instant, which is what the seconds and milliseconds values represent.
Is the live clock synced to a time server?
No — it reads your own device clock once per second. If it looks wrong, your system time or timezone setting is the place to check. No network request is made by this page.