Seconds and milliseconds are mixed
Using 10-digit and 13-digit timestamps incorrectly can shift dates dramatically.
Copy the seconds or milliseconds row according to your API contract.
Timestamp Converter
Convert Unix timestamps in seconds or milliseconds to local, UTC and ISO time, or generate timestamps from a date. All conversion is local and free.
Timestamp Converter overview
Timestamp Converter changes Unix seconds or milliseconds into local time, UTC and ISO 8601, and converts date input back to timestamps. It is useful for logs, APIs and timezone checks.
How to use Timestamp Converter
- 1Paste a seconds or milliseconds timestamp into the Unix timestamp input.
- 2Review milliseconds, seconds, local time, UTC and ISO outputs in the result panel.
- 3To generate a timestamp, choose a date and time in Date/time to timestamp, then click Convert.
- 4Click Current time to refresh the page to the browser's current timestamp.
Troubleshooting
UTC differs from local time
UTC strings and local displays are expected to differ by time zone offset.
Compare UTC, ISO and local rows together.
Date input uses local time
datetime-local does not include a time zone and is parsed in the browser time zone.
Use UTC or ISO output for cross-region work.
Seconds, milliseconds and ISO time compared
Most timestamp bugs come from unit or time zone confusion.
| Format | Shape | Common use | Notes |
|---|---|---|---|
| Unix seconds | About 10 digits | Backend logs and Unix tools | Often multiplied by 1000 for JavaScript Date |
| Unix milliseconds | About 13 digits | JavaScript Date.now and web events | Common in front-end analytics |
| UTC time | GMT/UTC string | Cross-time-zone records | May differ from local display |
| ISO 8601 | 2026-05-13T...Z | APIs, databases and logs | Z means UTC |
Timestamp Converter examples
Milliseconds timestamp conversion
Input
1715587200000
Output
Milliseconds, seconds, local time, UTC and ISO 8601 values
The tool detects seconds vs milliseconds automatically.
Use cases
Log debugging
Convert Unix timestamps from logs into local readable time.
API testing
Generate seconds or milliseconds values for expiry and event fields.
Time zone checks
Compare local, UTC and ISO output to avoid time zone mistakes.
FAQ
Is timestamp input uploaded?›
No. Conversion and formatting run locally in your browser.
How do I know seconds vs milliseconds?›
About 10 digits usually means seconds. About 13 digits usually means milliseconds. The tool detects this automatically.
Which time zone is used?›
Local time uses your browser time zone. UTC and ISO outputs are also shown.
Why is the result eight hours different from my server?›
That usually means you are comparing UTC with a UTC+8 local display.
Can I convert negative timestamps?›
Yes, as long as the browser Date range can represent them.
What does Z mean in ISO 8601?›
Z means the timestamp is in UTC, not local time.
Is the tool free?›
Yes. It is free and does not require sign-in.
Why does date input generate milliseconds?›
JavaScript Date uses milliseconds. The result panel also provides seconds for systems that need it.