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Excel Date Converter

Excel serial numbers to dates and dates to serials — 1900, 1904 and Google Sheets.

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Quick Tool Overview

The Excel Date Converter turns spreadsheet serial numbers into dates and dates back into serials, with times, in the Excel 1900, Excel 1904 and Google Sheets date systems, one value per line.

What it does
Converts Excel serials to dates and back
You give it
Serial numbers, dates or a mixed column
You get back
Dates or serials aligned with your input
Best for
Fixing CSV exports and database imports
Converters Free, unlimited use No sign-up Runs in your browser

About the Excel Date Converter

Spreadsheets store a date as a count of days, and a time as a fraction of a day, which is why a date column pasted into a text file, exported to CSV or imported from a database can turn into numbers such as 45000 or 45916.5. Turning them back needs the right starting point, and there are three.

Paste serials, dates or a mix of both, one per line. Numbers become dates and dates become serials, including the time of day. Choose Excel for Windows (the 1900 system), legacy Excel for Mac (1904) or Google Sheets and LibreOffice, and how ambiguous dates such as 03/04/2026 should be read. The converter reproduces Excel’s famous phantom 29 February 1900, so its serials match exactly what Excel shows.

Key features of the Excel Date Converter

Both directions at once

Numbers become dates and dates become serials in the same list.

Three date systems

Excel for Windows, legacy Excel for Mac and Google Sheets or LibreOffice.

Matches Excel exactly

Reproduces the phantom 29 February 1900, so early serials agree with what Excel displays.

Times included

Fractional serials become times of day, and dates with times become fractional serials.

Day-first or month-first

Choose how ambiguous dates like 03/04/2026 are read.

How to use the Excel Date Converter

  1. 1

    Paste the values

    Serial numbers, dates, or both — one per line.

  2. 2

    Pick the date system

    Excel 1900 for Windows, 1904 for old Mac files, or Google Sheets.

  3. 3

    Set date reading and output

    Day-first or month-first input, and the date format you want back.

  4. 4

    Copy the column

    Converted values line up with your input, ready to paste back.

Frequently asked questions

15 March 2023 in both Excel for Windows and Google Sheets.

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