UNIX timestamps count seconds since 1970-01-01 UTC. Many APIs use milliseconds instead. ISO 8601 is an interoperable string format.
Try the tool: Timestamp Converter
How to use the Timestamp Converter
- Enter a value in any field: UNIX seconds, UNIX milliseconds, or ISO 8601.
- The other fields update instantly with the converted values.
- Click Now to auto-fill the current time in all formats.
Examples
UNIX seconds → ISO 8601
1736070000 → 2025-01-05T12:20:00.000Z
Milliseconds → Human-readable
1736070000000 → Sunday, 05 Jan 2025 12:20:00 UTC
ISO 8601 → UNIX seconds
2025-01-05T12:20:00Z → 1736070000
Best practices
- Know your unit: Some APIs expect seconds, others milliseconds—double-check.
- Use UTC: Store timestamps in UTC and convert to local time only for display.
- ISO 8601: Prefer ISO strings (with timezone) for interoperability.
- Validate inputs: Guard against invalid dates and out-of-range values.
Common pitfalls
- Confusing seconds with milliseconds (factor of 1000).
- Assuming local timezone when the value is UTC (or vice versa).
- Relying on ambiguous date strings without timezone info.
FAQs
What’s the difference between seconds and milliseconds?
Seconds count whole seconds since the epoch; milliseconds are 1000× larger granularity. Multiply or divide by 1000 to convert.
Why does my ISO string show a different local time?
ISO times are commonly UTC (ending with Z). Your local time may differ by your timezone offset.
Do conversions happen locally?
Yes. Everything runs in your browser; no data is sent to any server.
How do I get the current timestamp?
Use the Now button in the tool or in code: Date.now() (ms) or
Math.floor(Date.now()/1000) (s).
👉 Try our free Online Timestamp Converter today.