How do I tell seconds from milliseconds?

By length. A current timestamp in seconds is ten digits; in milliseconds it is thirteen. If a date lands in 1970 you have divided by a thousand too many times, and if it lands tens of thousands of years hence you have not divided at all.

What time zone is a timestamp in?

None. It is a count of seconds since a fixed instant, identical everywhere. A zone only enters when the value is formatted for display, which is why storing timestamps and formatting late avoids so many bugs.

What is the year 2038 problem?

A signed 32-bit integer runs out on 19 January 2038, and systems still storing timestamps that way will overflow into 1901. Anything using 64-bit integers, which now includes most things, is fine for longer than the sun has left.

Are leap seconds accounted for?

No, and correctly so. Unix time deliberately ignores them: every day is treated as exactly 86,400 seconds, and a leap second is absorbed rather than counted. That is what makes the arithmetic simple and consistent everywhere.

Unix Timestamp Converter

Move between epoch seconds, milliseconds and readable dates.

Everything runs inside your browser. Your files never leave your device.

Input

Result

The result appears here as you type.

Ask about Unix Timestamp Converter

Questions about what this tool does, which option to pick, or what it can and cannot handle.

The question you type here is sent to an AI provider to be answered — your files and whatever you put in the tool above are not, and the assistant cannot see them. Answers are generated and can be wrong. The tool itself is not guessing: it runs deterministic code on your device.

About the Unix Timestamp Converter

A Unix timestamp counts seconds since midnight UTC on 1 January 1970. It is compact, unambiguous and completely unreadable, which is why it appears in logs, databases and API responses and why converting it is a daily task for anyone who works near them.

This converts in both directions. Give it a timestamp and it shows the date and time in UTC, in your local zone, as an ISO-8601 string and as a relative phrase — "four minutes ago", "in three days" — which is usually the fastest way to judge whether a value is what you expected. Give it a date and it returns the timestamp.

Seconds and milliseconds are distinguished automatically. JavaScript works in milliseconds, most other languages and most databases in seconds, and mixing them is the single most common bug in this area: a millisecond value read as seconds lands somewhere around the year 56000, and a seconds value read as milliseconds lands in January 1970. A timestamp of ten digits is seconds and thirteen is milliseconds, and the tool decides on that basis rather than making you specify.

The relative phrase deserves more credit than it gets. Reading 1735689600 tells you nothing at a glance. Reading "seven months ago" tells you immediately whether the record you are looking at is stale, whether the token has expired, and whether the cache entry should still be there. Most of the time that is the actual question.

Timestamps carry no time zone. A Unix timestamp is an instant, identical everywhere on Earth; the zone only appears when you format it for a person. Storing instants and formatting late is the practice that avoids an entire category of bug, and it is why the tool shows UTC and local side by side rather than picking one.

How to use it

1Paste a timestamp in seconds or milliseconds — the tool works out which from its length.
2Read the UTC time, your local time, the ISO-8601 form and how long ago it was.
3To go the other way, enter a date and read the timestamp back.
4When comparing two systems, compare in UTC. Local time hides an hour's difference twice a year.

Questions

How do I tell seconds from milliseconds?: By length. A current timestamp in seconds is ten digits; in milliseconds it is thirteen. If a date lands in 1970 you have divided by a thousand too many times, and if it lands tens of thousands of years hence you have not divided at all.
What time zone is a timestamp in?: None. It is a count of seconds since a fixed instant, identical everywhere. A zone only enters when the value is formatted for display, which is why storing timestamps and formatting late avoids so many bugs.
What is the year 2038 problem?: A signed 32-bit integer runs out on 19 January 2038, and systems still storing timestamps that way will overflow into 1901. Anything using 64-bit integers, which now includes most things, is fine for longer than the sun has left.
Are leap seconds accounted for?: No, and correctly so. Unix time deliberately ignores them: every day is treated as exactly 86,400 seconds, and a leap second is absorbed rather than counted. That is what makes the arithmetic simple and consistent everywhere.