Fundamentals
Unix Timestamps and Epoch Time, Explained Simply
What a Unix timestamp is, why it starts in 1970, and how to read and convert epoch time.
· 5 min read
A Unix timestamp is the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970 — a moment known as the Unix epoch. It is how most software stores and exchanges time.
Why 1970?
The epoch was chosen by the engineers building early Unix systems as a convenient recent starting point. It stuck, and now it underpins databases, APIs, and operating systems everywhere.
Seconds vs milliseconds
Unix timestamps are traditionally in seconds, but JavaScript and many APIs use milliseconds — a 13-digit number instead of 10. If your converted date lands in 1970 or far in the future, you probably mixed up the two.
Why engineers love it
- It is a single integer — easy to store, sort, and compare.
- It is timezone-independent, always counting from UTC.
- Arithmetic like "two hours later" is just adding 7200 seconds.
When you need a human-readable date, a timestamp converter turns the integer into a local date in any timezone you choose.