What is a Unix Timestamp Converter?
A Unix timestamp (also called epoch time) is a single number representing a point in time: the number of seconds that have elapsed since January 1, 1970, 00:00:00 UTC — an arbitrary reference point chosen when Unix systems were first designed. Computers store and compare dates as timestamps because a single number is trivial to sort, compare, and do arithmetic on, unlike a formatted date string. This tool converts between that raw number and a readable date, showing both UTC and your local timezone side by side, since timestamp values are always in UTC but you usually want to read them in your own timezone.
When to use it
You'll hit Unix timestamps constantly when reading API responses (created_at or expires_at fields are very often returned as raw epoch numbers), debugging why a JWT's exp claim seems wrong, setting up a cron job or scheduled task where you need to reason about specific future times, or querying a database where date columns are stored as timestamps. It's also useful when a log file shows raw timestamps and you need to quickly figure out what time an event actually happened.
How it works
Converting a timestamp to a date is simple multiplication and JavaScript's built-in Date object: seconds-since-epoch × 1000 gives milliseconds-since-epoch, which is what JavaScript's new Date() constructor expects. Converting the other direction — a picked date back to a timestamp — uses Date.getTime() and divides by 1000. The tricky part users usually run into isn't the math, it's units: some systems (like JavaScript itself) use milliseconds since epoch, while Unix and most backend systems use seconds — this tool shows both explicitly so you don't have to guess which one an API expects.
Frequently asked questions
Is a Unix timestamp in seconds or milliseconds?
Traditionally, Unix timestamps are in seconds — that's the original Unix/POSIX standard. However, JavaScript's Date.now() and many modern APIs use milliseconds instead. If a timestamp looks unexpectedly large (13 digits instead of 10), it's very likely milliseconds, not seconds.
Why is the date shown different between UTC and my local time?
A Unix timestamp represents one universal moment in time, but that same moment corresponds to different clock times depending on timezone — 00:00 UTC is a different local hour almost everywhere else in the world. This tool shows both so you can see exactly how the timestamp maps to your own timezone.
What happens when Unix timestamps run out in 2038?
This is the '2038 problem' — systems that store timestamps as a 32-bit signed integer will overflow on January 19, 2038, wrapping around to a negative number. Modern systems use 64-bit integers for timestamps, which pushes the same limit out roughly 292 billion years, so this only affects older 32-bit systems.
Can Unix timestamps represent dates before 1970?
Yes, as negative numbers — a timestamp of -86400, for example, represents December 31, 1969. Most modern systems and this tool handle negative timestamps correctly, though some older or stricter systems may not.