Unix Timestamps Explained

What is a Unix Timestamp?

A Unix timestamp (also called Epoch time) is the number of seconds that have elapsed since January 1, 1970, at 00:00:00 UTC. It's a simple, timezone-agnostic way to represent a point in time as a single integer.

1704067200  →  January 1, 2024 00:00:00 UTC
1000000000  →  September 9, 2001 01:46:40 UTC
0           →  January 1, 1970 00:00:00 UTC (the Epoch)

Seconds vs Milliseconds

Some APIs use seconds (10 digits), while JavaScript's Date.now() returns milliseconds (13 digits). Always check which format an API expects.

// JavaScript
Date.now()                    // 1704067200000 (milliseconds)
Math.floor(Date.now() / 1000) // 1704067200    (seconds)

// Convert timestamp to date
new Date(1704067200 * 1000)   // Mon Jan 01 2024...

Common Mistakes

• Mixing seconds and milliseconds: Passing seconds to new Date() gives a date in 1970.
• Y2K38 problem: 32-bit signed integers overflow on January 19, 2038. Use 64-bit timestamps.
• Timezone confusion: Unix timestamps are always UTC. Convert to local time for display.

Convert timestamps with our Timestamp Converter or calculate date differences with the Date Difference Calculator.