In the Calendar widget in Campaign Events, when clicking on a date that is in the following month (example, it is the June monthly calendar, but clicking on July 1 at the end of the month), the calendar will incorrectly select one extra month in advance. For example, clicking on July 1st in the June calendar, will currently select August 1st instead.

see attached video:

I am not sure where to put this ticket - @Mooeypoo recommended OOUI.

notes from @matmarex:
in mw.widgets.datetime.CalendarWidget.prototype.onDayClick, calling setFocusedDate "advances" the calendar by a month and the next call to setSelected uses the wrong month because of that