Unix Timestamp Converter (sec, ms, ISO, local)
Type a Unix timestamp to see the date in multiple formats, or pick a date to get its Unix value. Live current timestamp displayed for reference.
How it works
What a Unix timestamp is
A Unix timestamp is the number of seconds (or milliseconds, in JavaScript) since the Unix epoch — midnight UTC on 1 January 1970. It's a single number that encodes a moment in time without ambiguity. APIs, databases, and log files use it everywhere because comparing timestamps is just integer arithmetic.
JavaScript, Python, and many other systems use milliseconds (Date.now() returns ms in JS). C, Go, and Unix shells use seconds (date +%s). When converting, always check which unit your timestamp is in — a 1.7 trillion value is milliseconds; 1.7 billion is seconds.
ISO 8601 vs locale formats
ISO 8601 (e.g., 2026-05-06T14:30:00Z) is the universal interchange format. Time zone is explicit ('Z' = UTC, or +09:00 etc.), and it sorts correctly as text. Always use it for storage and APIs.
Locale formats (e.g., 'May 6, 2026, 2:30:00 PM') are for display. They depend on user language and region. The calculator shows both — copy ISO for code, copy locale for emails or reports.
The Year 2038 problem
32-bit signed integer Unix timestamps overflow at 2³¹ − 1 seconds = 2,147,483,647 = 03:14:07 UTC on 19 January 2038. Systems using int32 will roll over to negative values, breaking date arithmetic. Modern systems use 64-bit timestamps which are safe for ~292 billion years.
If you're working with embedded systems, old database schemas, or legacy C code, audit for time_t size. Migrating to 64-bit integers is the fix; storing timestamps as strings (ISO) avoids the issue entirely.
Frequently asked questions
›Why do timestamps sometimes have 13 digits?
Those are milliseconds. JavaScript and many web APIs use ms. Divide by 1000 to get seconds.
›What time zone is a Unix timestamp in?
None — it's UTC seconds since epoch. Convert it to a local date using the timezone your application or user is in.
›Is the conversion accurate?
Yes. We use the browser's Date API, which uses the system clock. Precision is to the millisecond.
›What's ISO 8601?
An international standard date-time format: YYYY-MM-DDTHH:MM:SS+TZ. Sortable as text, unambiguous about time zone.
›Why doesn't 'local time' match my system clock?
It uses your browser's reported time zone. If your system clock is wrong or the browser zone differs, results differ.
›Are negative timestamps valid?
Yes — they represent dates before 1970. Most languages handle them; be careful with database compatibility.
›Can I batch convert?
Not yet. For one-off conversions, this tool is fine; for thousands of values, use a script.
›Does the data leave my browser?
No. Conversion runs locally.
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