Excel serial number to date converter
If a sheet shows a number like 45292 instead of a date, enter it here to see the date it stands for; the decimal part is the time.
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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 serial number 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: for 61 and up, date = 1899-12-30 + serial; for 1 to 59, date = 1899-12-31 + serial; 60 is the fictitious 29 February 1900. 1904 system: date = 1904-01-01 + serial. Time = fraction × 24 h.
Example
Inputs: Serial number = 45,292.75, Date system = 1900 system (Windows, Google Sheets). Result: Date and time: 2024-01-01 18:00:00; Weekday: Monday; Note: 1900 system: serial 1 is 1900-01-01..
Limits and caveats
- A serial number carries no time zone, so the time shown is simply the time stored in the cell.
- The time is rounded to the nearest millisecond, as Excel does.
Questions about this tool
Why does Excel show my date as a number?
Excel stores dates as a day count from the start of its date system, and the cell is formatted as a number. Change the format to Date to see it normally.
What is the Excel 1900 leap year bug?
Excel treats 1900 as a leap year although it was not, so it has a 29 February 1900 at serial 60. Every serial before March 1900 is therefore one day off the true count.
When should I use the 1904 system?
For older Excel for Mac files that had the 1904 option on. If dates look 4 years and 1 day off, the file probably uses it.