Unix Timestamp Guide: Seconds, Milliseconds, and Timezones

Quick Answer

Quick Answer: Unix time is seconds since 1970-01-01 UTC (some APIs use milliseconds). Paste values into our Unix Timestamp Converter to see local and zoned times—always confirm whether your API uses 10- or 13-digit numbers.

Seconds vs milliseconds

JavaScript Date.now() returns milliseconds; many Linux logs use seconds.

Timezones

Epoch itself is UTC. Display layers apply zones—use the timezone selector in the converter when correlating with team-local incident reports. Pair with Timezone Converter for meetings.

Debugging workflow

1. Copy iat / exp from JWT Decoder
2. Convert in Unix Timestamp
3. Compare with server date output

Frequently Asked Questions

Why is my timestamp off by 1000×?

You likely treated milliseconds as seconds or vice versa.

Do timestamps include leap seconds?

Unix time ignores leap seconds; rare edge case for infra teams only.

Can timestamps be negative?

Yes—dates before 1970 have negative epoch values.