Developer Tools4 min read•Updated 2026-09-04
Unix Epoch Timestamp Conversion: Seconds, Milliseconds & UTC
Convert Unix timestamps to human-readable dates, local time zones, UTC, and ISO 8601 strings.
MX
MultiToolX Technical Team
Developer Productivity Engineering
Key Takeaways
- Unix timestamp is the number of seconds that have elapsed since Thursday, 1 January 1970 00:00:00 UTC (the Unix Epoch).
- JavaScript Date.now() uses milliseconds (13 digits), while Unix systems typically use seconds (10 digits).
- The Year 2038 Problem: 32-bit signed integers will overflow on 19 January 2038; 64-bit timestamps solve this.
1. Seconds vs Milliseconds Pitfall
A common bug in web development occurs when passing a 10-digit Unix timestamp (seconds) to JavaScript's new Date(timestamp), which expects milliseconds (13 digits). If your date resolves to January 1970, multiply by 1000!
Frequently Asked Questions
What is the Year 2038 problem?
On January 19, 2038, 32-bit signed integer timestamps will exceed 2,147,483,647 and wrap around to negative numbers. Modern 64-bit systems are immune.
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