Some events repeat on the last <weekday> of the month, e.g. "Monthly on the Last Saturday"
which will be either the 4th or 5th Saturday of a month
(because except for non-leap year Februaries, all months have 29, 30, or 31 days).
The Calendar: Repeats: Repeat Summary automatically chooses: Fourth or Fifth
depending on the particular month when the repeating event's start date is set,
unfortunately this design does not recognize that the event could be Last, rather than Fourth or Fifth.
I suggest the fix is to make it a manual choice of: First, Second, Third, Fourth, Fifth, or Last
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