Convert Unix timestamps to human-readable dates and back, with support for seconds, milliseconds, and multiple time zones. See the current timestamp update live.
——A Unix timestamp (also called Unix time, POSIX time, or epoch time) is a single number representing a specific point in time, counted as the number of seconds that have elapsed since 00:00:00 UTC on January 1, 1970 — a moment referred to as 'the Unix epoch.' Instead of storing a date as a year, month, day, hour, minute, and second, which requires interpretation and is ambiguous across time zones and calendar systems, a Unix timestamp reduces time to a single, unambiguous integer that increases steadily and uniformly, regardless of time zone, daylight saving time, or leap years.
This time-zone independence is the entire point: a Unix timestamp always refers to the exact same instant in time no matter where in the world it's read, which makes it the standard way computers store, compare, and exchange dates internally — the human-readable date you eventually see is just a formatted view of that underlying number, computed on demand for whatever time zone the viewer needs.
Unix timestamps solve several problems that plague human-readable date formats. Because it's a single integer, comparing two timestamps to see which came first is a simple numeric comparison, whereas comparing formatted date strings requires parsing and can be error-prone across different formats and locales. Storing dates as timestamps in a database is also more compact and efficient than storing formatted strings, and sorting records by date becomes a trivial numeric sort rather than a string-parsing operation.
Timestamps also sidestep time zone ambiguity entirely at the storage layer: a database column storing '1735689600' is unambiguous, while a column storing '2025-01-01 00:00:00' raises an immediate question — in which time zone? Systems typically store timestamps (implicitly UTC) and only convert to a human-readable, time-zone-specific string at the very last step, right before displaying it to a user, which is exactly the workflow this tool is built around.
Unix timestamps traditionally count seconds since the epoch, which was sufficient precision for most historical use cases and is still the standard in Unix/Linux systems, many databases, and older APIs. JavaScript, however, represents time internally using milliseconds since the epoch, a design choice made because JavaScript needed finer-grained timing for things like animations and performance measurement when it was created in the 1990s.
This difference is one of the most common sources of timestamp bugs: passing a seconds-based timestamp to a JavaScript function expecting milliseconds (or vice versa) produces a date that's off by a factor of 1,000 — typically resulting in a date near January 1, 1970, or a wildly far-future date. This tool's Seconds/Milliseconds toggle exists specifically to eliminate that ambiguity — always double-check which unit a timestamp is measured in before converting or comparing it.
Many older systems store Unix timestamps as a signed 32-bit integer, which can only represent whole numbers up to 2,147,483,647 — and a Unix timestamp reaches exactly that value at 03:14:07 UTC on January 19, 2038. After that instant, a 32-bit signed timestamp counter overflows and wraps around to a large negative number, which typically gets misinterpreted as a date back in December 1901, a bug now commonly known as the 'Year 2038 problem.'
Modern systems have largely solved this by migrating to 64-bit timestamp representations, which can represent dates roughly 292 billion years into the future. JavaScript's Date object has always used a 64-bit-range internally, so it isn't affected by the classic 2038 issue, but plenty of older embedded systems, legacy databases, and C programs using 32-bit time_t still are, which is why the 2038 rollover remains a real, actively-tracked migration concern in systems and infrastructure engineering.
Unix Timestamp Converter handles one specific date format. These related developer tools cover other conversions and encodings you'll often need alongside timestamps.