Understanding Unix Timestamps

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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, 00:00:00 UTC — a moment known as the Unix Epoch.

For example, the timestamp 1700000000 represents November 14, 2023 at 22:13:20 UTC.

Why Use Timestamps?

Unix timestamps solve several problems:

  • Timezone independence — a timestamp represents the same moment regardless of timezone
  • Easy comparison — comparing two numbers is simpler than comparing date strings
  • Compact storage — a single integer vs. a formatted date string
  • Universal standard — supported by every programming language

Timestamps in Different Languages

// JavaScript (milliseconds)
Date.now()                    // 1700000000000
Math.floor(Date.now() / 1000) // 1700000000

# Python
import time
time.time()  # 1700000000.123

// PHP
time();  // 1700000000

// Go
time.Now().Unix()  // 1700000000

The Year 2038 Problem

32-bit signed integers can store timestamps up to 2,147,483,647 (January 19, 2038 at 03:14:07 UTC). After this point, the value overflows and wraps to a negative number, potentially causing systems to interpret the date as December 13, 1901.

Modern 64-bit systems handle timestamps far beyond this limit, but legacy 32-bit embedded systems may need updates.

Convert Timestamps

Use our Unix Timestamp Converter to convert between timestamps and human-readable dates, with support for both seconds and milliseconds.