DatePicker appears to interpret DayFormat as a .NET DateTime format string when it shouldn't

[PathogenDavid]

Environment

Observed with XamlControlsGallery (with both 0.10.0-preview5 and the latest Avalonia CI build.)

Windows 10 2004

The Problem

The DatePicker control appears to be incorrectly using its DayFormat as a .NET DateTime format string:

I did not modify the example XAML, but here it is for reference:

<DatePicker x:Name="Control2" DayFormat="{}{day.integer} ({dayofweek.abbreviated})"
                               YearVisible="False" />

[amwx]

This is either a copy pasta mistake from the actual WinUI controls gallery or was created from a very early version of the DatePicker PR when I had originally tried to keep the WinUI formatting style (which was removed by request)
@danwalmsley

DatePicker Day/Month/YearFormat properties require the format to be in normal .net datetime formatting, for example for the equivalent from winui (from above) it would be DayFormat="d (ddd)"

[PathogenDavid]

In that case this issue should probably be moved to https://github.com/AvaloniaUI/XamlControlsGallery/ and reworded to fix the example.