Question 1

What is a Unix timestamp?

Accepted Answer

A Unix timestamp is the number of seconds (or milliseconds) since January 1, 1970 00:00:00 UTC, also called the Unix epoch.

Question 2

Seconds vs milliseconds — how do I tell?

Accepted Answer

Seconds timestamps are 10 digits (e.g. 1704067200). Milliseconds are 13 digits (e.g. 1704067200000). JavaScript Date.now() returns milliseconds.

Question 3

What timezone is used?

Accepted Answer

Unix timestamps are always UTC-based. The tool displays your local timezone alongside UTC for convenience.

Question 4

Why is my timestamp showing 1970?

Accepted Answer

You may have selected the wrong unit. A millisecond value interpreted as seconds will show a date near 1970.