Timestamp

A Unix timestamp (also called Epoch time or POSIX time) is the number of seconds that have elapsed since January 1, 1970, 00:00:00 UTC. It provides a universal way to represent a point in time as a single number, independent of time zones. For example, the timestamp 1700000000 represents November 14, 2023 at 22:13:20 UTC.

The Unix Epoch is the reference point for Unix timestamps: January 1, 1970, 00:00:00 UTC (timestamp 0). This date was chosen as the starting point when Unix was being developed in the late 1960s. All Unix timestamps are measured as seconds before or after this point.

The Year 2038 problem (Y2K38) occurs because many systems store Unix timestamps as signed 32-bit integers, which can hold a maximum value of 2,147,483,647. This corresponds to January 19, 2038 at 03:14:07 UTC. After this moment, the integer overflows and wraps to a negative number, potentially causing systems to interpret the date as December 13, 1901. Modern systems use 64-bit integers to avoid this issue.

Unix timestamps are traditionally measured in seconds since the epoch. However, many programming languages and APIs (especially JavaScript) use milliseconds instead, which is 1000 times the second value. This tool auto-detects whether your input is in seconds or milliseconds based on the magnitude of the number.

Unix timestamps are always in UTC by default — they represent an absolute moment in time. When you convert a timestamp to a human-readable date, you can choose which timezone to display it in. The underlying timestamp value does not change; only the displayed date and time adjust based on the selected timezone offset.