What is a Unix Epoch Timestamp?
The Unix timestamp (also known as POSIX time or Unix Epoch time) is the number of seconds that have elapsed since Thursday, 1 January 1970 00:00:00 Coordinated Universal Time (UTC), minus leap seconds. It provides a standardized, universal numerical timestamp across different operating systems, databases, and programming languages.
Seconds vs. Milliseconds
A frequent stumbling block for developers is distinguishing seconds from milliseconds:
- 10-digit timestamps (e.g.,
1700000000): Represent seconds. Commonly used in Linux system tools, Python (time.time()), PHP, and SQL databases. - 13-digit timestamps (e.g.,
1700000000000): Represent milliseconds. Standard in JavaScript (Date.now()) and Java.
This tool automatically detects whether your input is in seconds or milliseconds and displays conversions in UTC, ISO 8601, and your local browser timezone.
The Year 2038 Problem (Y2038)
On 19 January 2038 at 03:14:07 UTC, 32-bit signed integers will overflow, reaching their maximum value of 2,147,483,647 and wrapping into negative numbers. Modern 64-bit systems represent timestamps using 64-bit integers, effectively future-proofing systems for hundreds of billions of years.