Unix Timestamps Explained — Concepts and Conversion

What Is a Unix Timestamp?

A Unix timestamp (also called Epoch time or POSIX time) is the number of seconds that have elapsed since January 1, 1970 at 00:00:00 UTC. This reference point is called the "Unix Epoch."

Examples

• 0 = January 1, 1970, 00:00:00 UTC
• 1000000000 = September 9, 2001, 01:46:40 UTC
• 1710547200 = March 16, 2024, 00:00:00 UTC

Why Use Unix Timestamps?

1. Universal — no time zone confusion; the same number means the same moment everywhere
2. Sortable — events can be ordered with a simple integer comparison
3. Compact — a single integer instead of a formatted date string
4. Language-agnostic — every programming language can handle an integer

Using Unix Timestamps in JavaScript

// Current timestamp (seconds)
Math.floor(Date.now() / 1000);

// Convert a timestamp to a Date object
new Date(timestamp * 1000);

// Convert a date to a timestamp
Math.floor(new Date('2026-03-16').getTime() / 1000);

The Year 2038 Problem

Unix timestamps stored as signed 32-bit integers will overflow on January 19, 2038. Modern systems use 64-bit integers, which will not overflow for approximately 292 billion years.

Milliseconds vs Seconds

• Unix timestamp (seconds): 1710547200 — 10 digits
• JavaScript timestamp (milliseconds): 1710547200000 — 13 digits

If a timestamp has 13 digits, it is in milliseconds. Divide by 1000 to get seconds.

Convert Now

Use the free Unix Timestamp Converter to instantly convert between Unix timestamps and human-readable dates.