Unix Timestamp Converter
Convert Unix timestamps into readable dates and dates back into timestamps. The current epoch time ticks live at the top, and both seconds and milliseconds are detected automatically.
What Unix time is
Unix time counts the seconds elapsed since 00:00:00 UTC on 1 January 1970, known as the epoch. It is a single integer with no time zone, no daylight saving, and no calendar ambiguity, which is precisely why systems store time this way. All the messy human formatting happens only when the value is displayed.
Seconds or milliseconds?
Unix timestamps are conventionally in seconds, but JavaScript's Date.now() returns milliseconds, and mixing the two is one of the most common date bugs there is. A 10-digit number is seconds; a 13-digit number is milliseconds. Get it wrong by a factor of 1000 and your date lands in 1970 or somewhere around the year 55,000. This converter detects the length and interprets it correctly.
The 2038 problem
Systems that store Unix time in a signed 32-bit integer overflow on 19 January 2038, at which point the value wraps to a negative number and the date jumps to 1901. It is the same class of bug as Y2K. Modern 64-bit systems are unaffected — they are good for roughly 292 billion years — but embedded devices, older databases, and legacy file formats still carry the risk. If you are choosing a column type today, use a 64-bit integer or a native timestamp type.
Store UTC, display local
The rule that avoids most date bugs: store timestamps in UTC and convert to the user's time zone only at the moment of display. Storing local times means daylight saving transitions create times that occur twice and times that never occur at all, and a server move silently shifts your historical data. This tool shows UTC, ISO 8601, and your browser's local time together so you can see exactly how a value is being interpreted.