Date to Excel serial number converter
Useful when a formula or data import needs the numeric date value exactly as Excel understands it.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter date, time, seconds and date system.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
1900 system: serial = days since 1899-12-30, minus 1 for dates before 1900-03-01. 1904 system: serial = days since 1904-01-01. Then add time / 86400 seconds.
Example
Inputs: Date = 2024-01-01, Time = 18:00, Seconds = 0, Date system = 1900 system (Windows, Google Sheets). Result: Serial number: 45292.75.
Limits and caveats
- The fraction is shown to 8 decimals, which is finer than one second.
- Excel stores no time zone, so enter the time exactly as you want it to appear in the cell.
Questions about this tool
What is the serial number for today?
Pick today in the tool, or type =TODAY() in Excel and format the cell as a number.
How does Excel store time?
As a fraction of a day: 0.5 is 12:00 noon and 0.75 is 18:00.
Why is one day taken off before March 1900?
Excel counts a 29 February 1900 that never existed, so its serials before that day are one lower than a true day count.