What Is Unix Epoch Time?
Unix epoch time, also called Unix time or POSIX time, is a way of tracking time as a single running total of seconds since 1970. The epoch is defined as 00:00:00 on January 1 1970 in UTC (Coordinated Universal Time), and a timestamp is simply the number of seconds since 1970 that have elapsed since that moment. Because it is measured in UTC, epoch time is the same everywhere on Earth regardless of local time zone, which is exactly why developers rely on it.
Convert a Unix Timestamp to a Date
Paste a Unix timestamp into the "Timestamp to Date" box to turn it into a readable calendar date and time. The converter shows the result in both UTC and your own local time, so you can see the universal value and what it means where you are. Leave the unit set to "Auto" and it will detect whether your value is in seconds or milliseconds, or pick a unit yourself.
Convert a Date to a Unix Timestamp
Use the "Date to Timestamp" box to go the other way. Choose a date and time, decide whether it should be read as your local time or as UTC, and the converter returns the matching epoch time in seconds and in milliseconds. This is handy when you need to hard-code a timestamp for an API request, a database record, or a scheduled job.
Seconds vs Milliseconds
Epoch time appears in two common resolutions. A 10-digit number is a timestamp in seconds, while a 13-digit number is a timestamp in milliseconds (one thousand milliseconds per second). Many programming languages and JavaScript in particular work in milliseconds, whereas databases and Unix tools often use seconds. If a converted date lands far in the future or the distant past, you have almost certainly mixed up the two units.
Why Epoch Time Is Used
Epoch time is popular in computing because it is a single, unambiguous number. It is timezone-independent, easy to compare and sort, and simple to store in databases as an integer. APIs use it to timestamp events, log files use it to record when things happened, and applications use it to schedule work. For developers, doing arithmetic on epoch time, such as adding an hour or finding the gap between two events, is far easier than parsing formatted date strings.
