Unix Timestamp Explained: What It Is and How to Use It

What is a Unix Timestamp?

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

Timestamps are timezone-independent — they represent the same instant worldwide. This makes them ideal for databases, APIs, logging, and any system that needs to store or compare dates without ambiguity.

// Current timestamp (July 12, 2026)
1783766400  // seconds since epoch

// What it represents:
// Jan 1, 1970 00:00:00 UTC  +  1783766400 seconds
// = July 12, 2026 00:00:00 UTC

Seconds vs Milliseconds

Most systems use seconds, but JavaScript uses milliseconds. This is the most common source of bugs when working with timestamps across languages.

// JavaScript: seconds ↔ milliseconds
const nowSeconds = Math.floor(Date.now() / 1000);
const nowMillis = Date.now() * 1000;

// Python: convert to timestamp
import time
print(int(time.time()))  # 1783766400

Usage Across Languages

// JavaScript: create Date from timestamp
const date = new Date(1783766400 * 1000); // seconds to ms
console.log(date.toISOString()); // "2026-07-12T00:00:00.000Z"

// Python: timestamp to date
from datetime import datetime
dt = datetime.fromtimestamp(1783766400)
print(dt.strftime('%Y-%m-%d %H:%M:%S'))  # 2026-07-12 00:00:00

// SQL: store and query with timestamps
INSERT INTO events (name, created_at)
VALUES ('signup', 1783766400);

SELECT * FROM events
WHERE created_at > 1783700000;

The Year 2038 Problem

Systems using 32-bit signed integers for Unix timestamps will overflow on January 19, 2038. The maximum 32-bit signed value is 2,147,483,647, which corresponds to 03:14:07 UTC on that date.

Most modern systems already use 64-bit integers, which won't overflow for approximately 292 billion years. However, legacy code, embedded systems, and some databases may still be affected.