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Excel Date Converter

Turn the five-digit numbers Excel stores for dates into readable dates, or turn a date into its serial number, one value per line.

Processed locally in your browser

Options
A number becomes a date, and a date or date-time becomes an Excel serial number. Each line is detected on its own; no time zone is applied.0 chars · 0 lines
The result will appear here.

What is Excel Date Converter?

Excel does not store a date as text. It stores the number of days since a starting point, so 45292 is 1 January 2024, and the time of day is the fractional part: 45292.5 is noon. When a CSV export, a database column or a formula result shows 45292 instead of a date, this converter tells you the date, and it also goes the other way.

Each line is detected on its own: a number is read as a serial, while ISO dates, YYYY/MM/DD, DD/MM/YYYY (with an option for day-first), times such as 1:45 PM and date-times like 2024-01-15 13:45 become serial numbers. The tool follows Excel’s real rules, including the fictitious 29 February 1900, and flags zero, negative and too-large values. All calculation is plain integer day arithmetic, so there is no time zone or daylight-saving effect.

How does it work?

  1. Paste one value per line: a serial number like 45292.5 or a date such as 2024-01-15 13:45.
  2. Choose the date system: 1900 for workbooks made on Windows (the default), 1904 for old Mac workbooks.
  3. Turn on day-first if dates like 03/04/2024 mean 3 April rather than March 4.
  4. Read the table: result, weekday and a note for each line, including warnings about the 1900 leap-year quirk and out-of-range values.

Common use cases

  • Decoding a date column that shows 45000-style numbers after a CSV import or a copy from a database.
  • Checking what serial number to put in a cell or a test fixture for a given date and time.
  • Finding out why dates in a workbook received from a Mac are exactly four years and one day off.
  • Verifying a formula such as =A2-B2 or =WORKDAY(...) by converting its raw serial results back to dates.

Examples

Try this input in the tool above:

Input
45292
45292.5
60
2024-01-15 13:45
2024/03/01
0
Output
2024-01-01
2024-01-01 12:00:00
1900-02-29
45306.5729166667
45352
1900-01-00

Privacy

Excel Date Converter runs entirely in your browser. The text or files you provide are processed on your device and are not uploaded, logged or stored on our servers.

Limitations

Only dates from 1900-01-01 (1900 system) or 1904-01-01 (1904 system) to 9999-12-31 exist as serials. Time zones are ignored because serials are local wall-clock values, and text with month names is not parsed.

Frequently asked questions

Why does Excel think 29 February 1900 exists?

Early Lotus 1-2-3 counted 1900 as a leap year, and Excel copied the behaviour for compatibility. As a result serial 60 is a date that never existed, and serials 1 to 59 are one day earlier than the real calendar arithmetic from 1899-12-30. From serial 61 (1 March 1900) everything matches the real calendar.

What is the 1904 date system and when does it matter?

Excel for Mac used to start counting on 1 January 1904, so each serial is 1,462 days lower than in the 1900 system. Copying dates between workbooks that use different systems shifts them by four years and one day. You can check the setting under File, Options, Advanced, "Use 1904 date system".

How is the time of day stored?

As the fraction after the decimal point: 0.5 is 12:00, 0.25 is 06:00 and 0.999988 is just before midnight. The serial holds no time zone, so an ISO date with Z or an offset is converted as written and the offset is ignored.

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