Hi @AlexanderBlackman Tnx for your Great PR.
I have no problem with breaking changes because we are currently in preview.
Changing names is also great.
I saw some things that needed to be fixed.
First, please revert the Git Ignore items to their previous state. i think This action was probably unintentional.

9ed50c0

Regarding the following code, it is likely to end up in an infinite loop.

private void CalendarWithClock_SelectedTimeChanged(object sender, DateTimeOffset e)
{
    if (calendarWithClock != null)
    {
        SelectedDateTime = e;
        SelectedTime = e.TimeOfDay;
    }
    SelectedTimeChanged?.Invoke(this, e);
}

Assigning a new value to SelectedTime triggers OnSelectedTimeChanged, which calls UpdateSelectedTime(). This method updates calendarWithClock.SelectedTime.
if SelectedDateTime or SelectedTime is changed within CalendarWithClock_SelectedTimeChanged, the associated property-changed callback will run. This could cause the CalendarWithClock properties (SelectedDateTime or SelectedTime) to be updated again, potentially resulting in a loop.

do we need to Update SelectedDateTime/SelectedTime in SelectedTimeChanged? I haven't seen any problems with the tests before.
If there are circumstances where this is necessary, please Ensure updates only occur when necessary to avoid unnecessary callbacks.
something like:

if (SelectedDateTime != e)
    SelectedDateTime = e;

if (SelectedTime != e.TimeOfDay)
    SelectedTime = e.TimeOfDay;

Thank you for your suggestions, I only checked for loops via the debugger, as I didn't want to add a new test project.

I assumed this wouldn't a infinite loop, as the event is triggered by CalendarWithClock's SelectedDateTime changing, and not DateTimePicker. But you are right, it might cause problems, so I've copied your try-finally isUpdating = false wrapping.

When stepping through with debugger, MicaSystemBackdrop's OnDefaultSystemBackdropConfigurationChanged is called many many times, but I'm assuming that's work-in-progress, so I stayed clear.

Sorry for the gitignore changes, I think it happened automatically when I just tried to change the DevWinUI.Controls project on its own as at the time I hadn't installed VS Preview and couldn't open slnx. I'll be more careful next time, this is the first time I've contributed on Github for years.

LGTM🚀
Thank you for addressing the feedback.
I would be happy if you could work on MicaSystemBackdrop's issue.
I'm currently focused on controls and trying to bridge the gap between WPF and WinUI.
I'm currently working on a carousel control and I'm planning to create something similar to the Microsoft Store Carousel.
That's why I can't work on fixing these problems right now because it will probably take more time.

Good suggestion, but I'm not too familiar with backdrops.
I'm currently experimenting with making the DateTimePicker being settable and bindable.
Originally the clock's default time overwrote it, but I seem to have fixed it.

Here's me using DateTimePicker to edit an existing appointment in a scheduler.


The colours are deliberately ugly, sorry.