Hi Mary and Welcome to the Board,
This thread has example code that should do what you describe.
Pivot table with data validation
PivotFilters.Add works a little differently. Instead of making individual PivotItems Visible or Hidden, it uses a criteria string. That function would be a better fit if you wanted all dates after a specified date, or between a pair of dates.
Just ask if you need any help adapting the code for your purpose.