Datepicker opendays set from monday->saturday, and week starting on monday => this results in mondays unavailable for selection.
After altering opendays from sunday->friday (thus not including saturday) behaviour is as desired: mo-tu-we-th-fr-sa are available, sunday not selectable.
Seems a bug to me?
I have disabled Sunday in the Open Days and I still could select Monday when it's the first month day:
is this the problem you are having ?
