Timestamp Converter
Turn a Unix timestamp into a date you can read, or a date into a timestamp. It tells you whether it read your number as seconds or milliseconds.
Processed on your device — no upload
A ten-digit number is seconds and a thirteen-digit one is milliseconds — the same instant written two ways, and the reason a timestamp pasted into the wrong field lands in the year 56000. Which one you gave it is stated above rather than guessed at silently.
How to use it
- Paste a timestamp, or a date like 2025-01-01.
- Read it back as Unix seconds, milliseconds, ISO 8601, UTC and your own time zone.
- Tap any line to copy it.
How it works
A Unix timestamp counts the seconds since midnight UTC on 1 January 1970 — a date chosen because it was recent and round when Unix was being written, not for any deeper reason. It is the format almost every system stores a moment in, because a single integer has no time zone, no daylight saving, no calendar and no ambiguity about what 03/04/2025 means.
The catch is the unit, and it is the reason this tool exists. Unix counts seconds. JavaScript, Java and most databases count milliseconds. Postgres and Chrome's internals sometimes count microseconds. They are all called timestamps, they all look like a long number, and pasting one into a field expecting another does not produce an error — it produces a date in 1970 or a date in the year 56000, quietly.
The number is read by its magnitude, which is what every converter does and is right in practice: a seconds value large enough to be mistaken for milliseconds would be a date in the year 5138. What is different here is that the reading is stated on screen rather than applied silently, so if it guessed wrong you can see that it did.
Dates before 1970 are negative, and they work. So does the epoch itself, which is 0 — a value worth remembering, because a date field showing 1 January 1970 almost always means something sent a zero rather than a date.
Your local time is rendered from your browser's own time zone, which is read from your system settings and never sent anywhere. Nothing you type here leaves the page.
A worked example
A log line reads "expires_at": 1735689600 and you need to know whether that has already passed.
Paste it. The tool says read as seconds and gives you Wednesday, 1 January 2025 at 00:00:00 in your own time zone, along with the relative reading — 7 months ago, or however long it has been when you read this. That relative line is usually the whole question.
Now the other direction — date to timestamp. A form wants one and you have a date. Type 2025-01-01 and it comes back as 1735689600 in seconds and 1735689600000 in milliseconds. Copy whichever the field wants — and if you do not know which, the length is the tell: ten digits is seconds, thirteen is milliseconds.
A note on the last case. 2025-01-01 with no time is read as midnight UTC, not midnight where you are. If you need midnight in your own zone, write it out: 2025-01-01T00:00:00 without the Z.
Questions
Is my timestamp in seconds or milliseconds?
Count the digits. Ten digits is seconds for any date in this century; thirteen is milliseconds; sixteen is microseconds. The tool works it out the same way and tells you which it used, so you can tell at a glance whether it read you correctly.
What is the Unix epoch?
Midnight UTC on 1 January 1970, the moment Unix time counts from. Timestamp 0. If a date field in some application is showing 1 January 1970, it is almost certainly receiving a zero rather than a date.
Can it handle dates before 1970?
Yes. They are negative — a timestamp of -86400 is 31 December 1969. Some systems reject negative timestamps entirely, which is worth knowing before you paste one into a form.
Why does my date come out an hour off?
Almost always daylight saving, and almost always because a date without a time zone was read as UTC. A timestamp itself has no time zone at all — it is a count of seconds — so the offset appears when it is rendered, not when it is stored.
What is the 2038 problem?
Systems that store Unix time in a signed 32-bit integer run out of room on 19 January 2038, at timestamp 2147483647, and wrap round to 1901. Most modern software uses 64 bits and is unaffected for about 292 billion years. Old embedded systems are the ones to worry about.
Does this send my data anywhere?
No. The conversion is arithmetic your browser does, and your time zone comes from your own system settings. The site is static files with no backend, so there is nothing to send anything to.
Is Timestamp Converter free to use online?
Yes — free, with no account, no daily limit and no watermark. It runs online in your browser, and because the work happens on your own device it keeps working offline once the page has loaded.
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