Unix Timestamps Explained Simply
What is a Unix timestamp, why does it start from 1970, and why it matters.
A Unix timestamp is one of the most fundamental concepts in computing — and also one of the most misunderstood. Here's everything you need to know.
What Is a Unix Timestamp?
A Unix timestamp is simply the number of seconds that have elapsed since January 1, 1970, at 00:00:00 UTC. This moment is called the Unix Epoch.
For example, the timestamp 1700000000 represents November 14, 2023, at 22:13:20 UTC.
Why January 1, 1970?
When Unix was being developed in the late 1960s and early 1970s at AT&T Bell Labs, the developers needed a reference point for time.
The exact date wasn't chosen for any profound reason — it was simply convenient at the time. By the first Unix manual in 1971, this had been refined to seconds from January 1, 1970.
The Year 2038 Problem
Traditional Unix timestamps are stored as a signed 32-bit integer, which can hold values up to 2,147,483,647.
That maximum corresponds to January 19, 2038, at 03:14:07 UTC. After that, 32-bit systems will overflow to negative numbers — interpreting the time as December 13, 1901.
Most modern systems now use 64-bit timestamps, which won't overflow for billions of years.
Unix Timestamps in Practice
Unix timestamps are used everywhere in computing: - Databases: storing when records were created or modified - APIs: transmitting dates in a language- and timezone-agnostic format - Log files: recording when events occurred - Cryptography: certificate expiration dates
Millisecond vs Second Timestamps
Some systems (notably JavaScript) use millisecond-precision Unix timestamps. To convert: - Seconds to milliseconds: multiply by 1,000 - Milliseconds to seconds: divide by 1,000
Our Unix timestamp tool handles both formats automatically.