Unix Timestamps: Everything You Need to Know
5 min read · Updated June 2026
A Unix timestamp is the number of seconds since January 1, 1970 00:00:00 UTC (the "Unix epoch"). It's the universal language of time in computing — every database, API, and logging system uses it.
Seconds vs Milliseconds
The #1 Source of Bugs
JavaScript uses milliseconds (13 digits). Most APIs use seconds (10 digits). Always check which one you're dealing with. A 10-digit timestamp in JavaScript gives a date in 1970.
- Seconds (Unix time) — 10 digits:
1718236800(June 13, 2024) - Milliseconds (JavaScript) — 13 digits:
1718236800000
Common Conversions
// JavaScript: Get current timestamp
Math.floor(Date.now() / 1000) // seconds
Date.now() // milliseconds
// JavaScript: Convert timestamp to date
new Date(timestamp * 1000) // if seconds
new Date(timestamp) // if milliseconds
// Python: Get current timestamp
import time; int(time.time()) // seconds
ISO 8601 Format
The human-readable standard for timestamps:
2026-06-13T12:00:00Z— UTC time (Z = Zulu)2026-06-13T08:00:00-04:00— With timezone offset (EDT)2026-06-13T12:00:00.123Z— With milliseconds
The Bottom Line
- Unix timestamps are seconds since 1970-01-01 00:00:00 UTC
- JavaScript uses milliseconds — always multiply/divide by 1000
- ISO 8601 is the standard format for APIs and logs
- Always store timestamps in UTC — convert to local time only for display
⏱ Convert timestamps Instantly
Use our Unix Timestamp Converter to convert between timestamps and readable dates — supports seconds, milliseconds, and ISO 8601.
Disclaimer: This guide is for informational purposes only.