When the UseMaterial3 MSBuild property is enabled, the DatePicker control should follow the Material 3 design system. However, the current implementation does not fully reflect Material 3 behavior.
The DatePicker should apply Material 3–specific styling, including the updated calendar layout, header, day/year selectors, navigation controls, and state visuals (hover, pressed, selected, disabled). It should also use the appropriate Material 3 theme resources to ensure visual consistency.