Unix Timestamp Converter

Unix time counts seconds since January 1, 1970 00:00:00 UTC — the "Unix epoch." Developers use it in APIs, databases, and log files because it is timezone-neutral at storage time. Display always requires picking a timezone for humans.

Some systems store milliseconds instead of seconds — 13-digit values are milliseconds; 10-digit values are seconds. This tool auto-detects based on magnitude.

Example: 1722384000 seconds = July 31, 2024 00:00:00 UTC. To convert back, pick a local date and time — the Unix value depends on your timezone offset from UTC.

Unix time deliberately ignores leap seconds, which makes it a count of a fixed 86,400 seconds per day rather than a true elapsed-time count. That is why it stays aligned with civil calendars and why it is not suitable for measuring precise intervals across a leap second — TAI or a monotonic clock is the right tool for that.

Digit count is a reliable way to identify the unit. Ten digits is seconds and lands in the current era; thirteen digits is milliseconds; sixteen digits is microseconds, common in database engines and tracing systems. Treating milliseconds as seconds throws a date roughly 50,000 years into the future, which is usually the giveaway.

The classic bug in this area is off-by-1000. JavaScript's Date.now() returns milliseconds while most Unix command-line tools, Python's time.time() truncation, and many APIs use seconds, so piping one into the other silently produces 1970 or a distant future date. Convert explicitly at every boundary rather than relying on auto-detection.

Storage is timezone-neutral but display never is, and that asymmetry causes most timestamp confusion. The same integer renders as two different dates for a user in Los Angeles and one in Berlin, so always label whether a rendered time is UTC or local civil time — particularly when correlating application logs with a user's report of when something happened.

Two range limits still matter in practice. Signed 32-bit timestamps overflow on January 19, 2038, which remains a live concern in embedded and legacy systems, and negative values represent dates before 1970 — valid in most modern libraries but a frequent source of errors in code that assumes an unsigned integer.

Millisecond timestamps are common in JavaScript (Date.now) while Unix tools often expect seconds — divide or multiply by 1,000 when piping data between systems.

Negative timestamps before 1970 are valid in many systems — confirm your library signedness when debugging legacy log files.

Leap seconds and timezone offsets do not change the underlying integer — always label whether you display UTC or local civil time.

Programming languages may store timestamps as 32-bit or 64-bit integers — watch for year 2038 overflow in legacy 32-bit systems.