Date & Time Tools
Convert between Unix time and human-readable dates in your browser.
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Seconds vs. milliseconds
Unix time is defined in seconds since 1970-01-01 00:00:00 UTC, but many languages and APIs (JavaScript's Date.now() among them) work in milliseconds instead, and mixing the two up is the single most common timestamp bug. The fix is usually just a digit count: a current seconds timestamp is 10 digits, the same moment in milliseconds is 13. If Unix Timestamp Converter gives you a date centuries away from where you expected, that mismatch is the first thing to check.
UTC vs. local time
A timestamp itself has no timezone, it's a fixed count of seconds from a fixed instant, but the human-readable date shown for it depends entirely on which timezone you're viewing it in. The same timestamp reads as one clock time in UTC and a different one in, say, US Eastern, and the gap shifts by an hour across a daylight saving transition. If two systems disagree on what a timestamp "means," check whether they're comparing it in the same timezone before assuming the timestamp itself is wrong.
The Year 2038 problem
Older systems that store Unix time as a signed 32-bit integer can only count up to 2,147,483,647 seconds past the epoch, which runs out on 2038-01-19. Past that point the value overflows and wraps to a large negative number, which reads back as a date in December 1901. This mostly matters for embedded systems, older 32-bit software, and some file formats and databases with a fixed 32-bit time field; modern JavaScript numbers (and this converter) aren't limited that way and represent dates far beyond 2038 without overflowing.
Frequently asked questions
- What is a Unix timestamp?
- The number of seconds (or, in some systems, milliseconds) elapsed since 1970-01-01 00:00:00 UTC, also called the Unix epoch. It's timezone-agnostic by definition; the moment it represents is fixed, and only the display format changes with timezone.
- How do I tell if a timestamp is in seconds or milliseconds?
- Check the digit count. Current dates in seconds are 10 digits (e.g. 1758067200); the same moment in milliseconds is 13 digits (1758067200000). Pasting a 13-digit value into a field expecting seconds lands tens of thousands of years in the future, and pasting a 10-digit value into a field expecting milliseconds lands in 1970, which is usually the tell that something's off.
- Why does converting the same timestamp give me different dates?
- A Unix timestamp is UTC by definition, but a converter can display it in UTC or in a local timezone, and those will show different clock times for the exact same instant. If a converted date looks off by a few hours, check whether the display is showing UTC or your local time, not the timestamp itself.
- Does this handle daylight saving time?
- Yes, when converting to a named local timezone. DST is resolved through the browser's Intl API, which knows each region's rules, so a local-time conversion already accounts for whether DST was in effect on that date.
- What is the Year 2038 problem?
- Classic Unix timestamps stored as a signed 32-bit integer overflow on 2038-01-19, wrapping around to a negative number that reads as a date in 1901. It mainly affects older or embedded systems still using a 32-bit time type; JavaScript's numbers, and this converter, use 64-bit precision and aren't subject to it.