Does it support milliseconds?

Yes. We auto-detect 10-digit seconds and 13-digit milliseconds for Unix → Date.

Yes. Choose Local format and provide an IANA timezone like America/New_York.

Yes. Only the values you convert are sent to the API; no storage. You can adapt to a client-only mode if needed.

Batch Unix Timestamp Converter – CSV upload and download

Paste or upload a CSV file to convert a list of values. Supports Unix seconds → ISO date and Date string → Unix seconds. Results can be downloaded as CSV.

How to use

Select conversion mode: Unix → Date or Date → Unix.
Paste values into the text area (first column), or upload a CSV file. The first row may be a header.
Click Start to convert. Preview results below.
Click Download CSV to export the results.

Notes

Unix timestamps are treated as seconds. If you have milliseconds (13 digits), divide by 1000 first.
Date parsing uses your browser (ECMAScript Date). Prefer ISO 8601 format for accuracy, e.g. 2023-10-11T00:00:00Z.
No data leaves your browser except the API request; you can also adapt to a client‑only mode.