What Is a Unix Timestamp? A Complete Beginner's Guide (2026)

Need to convert a Unix timestamp right now? Use the free Unix Timestamp Converter — paste any epoch value, get the date in 20 timezones, or convert a date back to epoch. No signup required.

What Is a Unix Timestamp?

A Unix timestamp (also called epoch time or POSIX time) is a single integer representing how many seconds have elapsed since January 1, 1970, 00:00:00 UTC.

For example: 1740000000 represents a specific second in history. Add 1 to get the next second. Timestamps are timezone-independent — the same number represents the same moment everywhere on Earth.

Why Does Unix Time Start on January 1, 1970?

Unix developers in the 1960s needed a reference point that predated all modern computers. January 1, 1970 was chosen as a practical convention. By starting before most computing, all real-world timestamps are positive integers, which simplifies arithmetic and storage.

The maximum 32-bit signed timestamp (2,147,483,647) corresponds to January 19, 2038 — the famous "Year 2038 problem." Modern systems use 64-bit timestamps, which extend the range billions of years into the future.

Seconds vs Milliseconds Timestamps

Two formats exist, and confusing them is a very common bug:

How to Get the Current Unix Timestamp

// JavaScript (milliseconds — divide by 1000 for seconds)
Math.floor(Date.now() / 1000)

// Python
import time; int(time.time())

// PHP
time()

// Bash/Linux
date +%s

// SQL (MySQL)
UNIX_TIMESTAMP()

// SQL (PostgreSQL)
EXTRACT(EPOCH FROM NOW())

How to Convert a Unix Timestamp to a Date

// JavaScript
new Date(1740000000 * 1000).toISOString()
// → "2025-02-19T22:13:20.000Z"

// Python
from datetime import datetime
datetime.fromtimestamp(1740000000)
// → datetime(2025, 2, 19, 22, 13, 20)

// PHP
date('Y-m-d H:i:s', 1740000000)
// → "2025-02-19 22:13:20"

Or use the free Unix Timestamp Converter — no code required. Supports 20 timezones and auto-detects seconds vs milliseconds.

Common Use Cases

• Storing dates in databases without timezone confusion
• Comparing two dates by simple integer subtraction
• API responses — most APIs return dates as Unix timestamps
• Session expiry, JWT token expiry, cache TTL
• Logging and analytics systems
• Scheduling future events (cron jobs, reminders)

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