Paste a Unix timestamp to see it as a date in UTC, in your local time zone and in ISO 8601 format, or go the other way and turn a date into a timestamp. Seconds and milliseconds are detected automatically, and the current timestamp ticks live at the top.
A ten-digit timestamp is seconds; thirteen digits is milliseconds. JavaScript's Date.now() returns milliseconds while most other languages, databases and APIs use seconds. Passing one where the other is expected puts your date either in January 1970 or roughly fifty thousand years from now, which is at least an obvious failure. This converter detects the unit from the digit count.
Unix time is defined as the number of seconds since the epoch assuming every day has exactly 86,400 seconds. Real leap seconds are absorbed by repeating or stretching a second rather than incrementing the counter, which keeps the arithmetic simple at the cost of the count not being the true number of elapsed SI seconds.
A signed 32-bit timestamp runs out on 19 January 2038 and wraps to a negative number, landing in 1901. Anything modern uses 64 bits and is safe for longer than the universe has existed, but embedded devices and old file formats remain a real migration problem.
The number of seconds elapsed since 1 January 1970 at 00:00:00 UTC, ignoring leap seconds. Because it is a single integer in UTC, it sidesteps time zones and formatting entirely, which is why it is used everywhere in software.
A 10-digit number is seconds; 13 digits is milliseconds. JavaScript works in milliseconds while most other languages and databases use seconds, which is a very common source of dates landing in 1970 or in the year 55000.
A signed 32-bit timestamp overflows on 19 January 2038 and wraps to a negative number, putting the date in 1901. Modern systems use 64-bit timestamps, which do not overflow for another 292 billion years, but legacy systems and embedded devices remain a concern.
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