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Excel Serial Date Converter

Convert Excel serial dates in the 1900 or 1904 system to ISO UTC and back.

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Rejects fictitious serial day 60 in the 1900 system. Fractions represent time of day; conversion rounds to milliseconds and assumes UTC.

Up to 100,000 UTF-16 units per input and 1,000,000 per result. See the supported formats and examples below.

How to use

  1. Convert Excel serial dates in the 1900 or 1904 system to ISO UTC and back.
  2. Choose the mode or options, then run the tool.
  3. Review the result, then copy or download the TXT file.

Example

25569.5 (1900 system) ⇄ 1970-01-01T12:00:00.000Z

Details and limitations

Rejects fictitious serial day 60 in the 1900 system. Fractions represent time of day; conversion rounds to milliseconds and assumes UTC.

Text stays in your browser; it is not sent to a conversion server.

FAQ

Excel Serial Date Converter — What are the supported inputs and limits?

Rejects fictitious serial day 60 in the 1900 system. Fractions represent time of day; conversion rounds to milliseconds and assumes UTC.

Format references

Tool page updated: