About Timestamp converter
A Unix timestamp counts the seconds since midnight UTC on 1 January 1970. It is compact, unambiguous, and completely unreadable — nobody looks at `1735689600` and thinks "New Year's Day 2025". This converts in both directions: paste a timestamp to get readable dates, or paste a date to get the timestamp.
Seconds or milliseconds is detected automatically. This is the most common source of confusion, because different ecosystems disagree. Unix tooling, Python's `time.time()`, PostgreSQL and JWT claims all use seconds. JavaScript's `Date.now()`, Java and most JSON APIs use milliseconds. The two differ by a factor of a thousand, so mixing them up puts you either in 1970 or somewhere around the year 56000. Detection is by magnitude: anything above roughly 1e11 is treated as milliseconds, which is reliable for any date in the modern era.
You get back Unix seconds, Unix milliseconds, ISO 8601 in UTC, RFC 2822, your local time with the timezone named explicitly, and a relative description like "3 days ago". The local rendering uses your browser's timezone, so it is the one line on this page that differs depending on who is looking — worth remembering before pasting it into a bug report someone else will read.
Going the other way, paste an ISO date like `2025-01-01T00:00:00Z` or most common date formats and you will get the timestamp. A date without a timezone is interpreted as local time, which is a frequent source of off-by-a-few-hours errors; append `Z` to force UTC.
On negative timestamps and the 2038 problem. Dates before 1970 are negative and handled correctly here. Separately, systems storing timestamps in a signed 32-bit integer overflow on 19 January 2038 — if you are debugging a date that lands there, that is very likely why. This tool uses 64-bit floats and has no such limit.
Questions
How does it know if my number is seconds or milliseconds?
By magnitude. Values above about 1e11 are treated as milliseconds, which is correct for any date in the modern era. The result names which interpretation it used.
Why is the local time different from what a colleague sees?
Local time uses your browser timezone, so it varies by viewer. The ISO and UTC lines are absolute — use those when sharing.
Can I convert a date back into a timestamp?
Yes. Paste an ISO date or most common date formats. A date with no timezone is read as local time, so add Z if you mean UTC.
Does it handle dates before 1970?
Yes. Those are negative timestamps and convert correctly.