When you select the start and end dates in the Pivot table grouping, make sure that you uncheck the "Auto" boxes to force the specified dates to eliminate the unwanted months. I tested this fine with you sample data.
In order to filter by month and year, create a custom filter on the data field whereby you select Date Filters > Custom Filter > is not between and then choose the begin date and end date for data not to be shown. This will allow you to filter out a particular month such as in your example.