I'm able to see a similar error when using DateTimeEditBox in the XAML Designer. While using Visual Studio 2022, I will see the error display from time-to-time after modifying the value of the "Value" property. The error appears to be generated by Visual Studio IntelliSense and does not prevent the application from compiling. When I close the XAML editor or compile the application, the error goes away. If I change the Error List settings to "Build Only", the error also goes away.
From what I'm seeing, this appears to be an issue with the Visual Studio XAML Designer IntelliSense and not an issue with our controls. While clearly distracting, it should not impact your ability to successfully compile and run your application.
Please let us know if your experience is not consistent with ours.