Convert between Excel serial numbers and real dates. Handles the 1900 leap year bug, the 1904 Mac system, and time fractions in the decimal. All processing runs locally in your browser. Your data is not uploaded to any server.
100% Local Processing
How to Use
Turn an Excel serial number into a real date, or a real date into the serial Excel expects. Both the 1900 and the 1904 systems are supported.
Steps
Enter a serial number such as 46000, or a date if you want the serial back.
Set the direction and the date system your spreadsheet uses.
Click Convert and read the result with the time fraction broken out.
The 1900 leap year bug
Excel wrongly treats 1900 as a leap year, so serial 60 is a phantom 29 February 1900.
This tool refuses serial 60 and tells you why, instead of returning a wrong date.
Serials from 61 upwards are shifted by one day to stay correct.
Serials from 1 to 59 map straight onto January and February 1900.
Features
The decimal part of a serial is treated as a fraction of a day.
The 1904 Mac system is supported alongside the 1900 Windows system.
ISO 8601 and Unix seconds are included for cross checking.
All processing runs locally in your browser. Your data is not uploaded to any server.