For 1970-01-01T00:00:00Z, Unix seconds and milliseconds are both 0. A local display may show a different clock time because of your device time zone.
BROWSER UTILITIES · FREE JAVASCRIPT TOOL
Unix Timestamp & Date Converter
Convert seconds, milliseconds and readable dates between local time, UTC and ISO 8601.
Free to useNo sign-upRuns in your browser
JS
Timestamp ConverterLocal browser processing
Ready in your browser
Your processed result will appear here.
A WORKED TASK
Compare seconds, milliseconds and time zones
Paste a Unix timestamp or an unambiguous ISO date. Compare the ISO 8601, UTC and local-time lines: they describe the same instant in different displays. For a predictable test, enter 1970-01-01T00:00:00Z rather than a date with no time-zone suffix.
This is a date conversion utility, not a calendar scheduler. Local results depend on the device’s time-zone settings, and fractional seconds can be rounded when shown as Unix seconds.
What to check
- Modern Unix timestamps commonly use 10-digit seconds or 13-digit milliseconds.
- The tool uses a magnitude heuristic for numeric input; unusually old or distant dates can be ambiguous.
- Prefer ISO dates with Z or an explicit offset. Short date strings can be interpreted differently across browsers.
TESTED & REVIEWED
Know what this tool does—and where to double-check
- Reviewed by
- HTML Online Viewer project
- Last reviewed
- Processing
- Ordinary processing happens in this browser tab; the tool does not intentionally upload your source.
- Important limitation
- JavaScript checks and transformations cannot prove that application logic is correct. Test the result in its real project before publishing.
PRACTICAL EXAMPLE
Start with a small Timestamp Converter example
The built-in sample makes the accepted input visible before you use your own project data.Example input
Loaded in the workspace
1788570000Run the sample first, then change one value at a time so each result remains easy to explain.
What this example demonstrates
Convert seconds, milliseconds and readable dates between local time, UTC and ISO 8601.
Keep the original file, review the generated result and test production code in its real application before publishing.
COMMON QUESTIONS
Timestamp Converter FAQ
Is Timestamp Converter free?
Yes. It is free to use and requires no account.
Does Timestamp Converter upload my source?
No. Ordinary processing happens locally in the current browser. The JavaScript runner uses a short-lived isolated browser worker.
Can I import and export a file with Timestamp Converter?
Yes. Import a relevant JavaScript, JSON or text file, then save the input or processed result.