As you say that the date property is available in different clipboard pages, my suggestion would be to write an Activity to fetch all the date property values from the different clipboard pages and then store it in the list then write the java code which can perform your filter to group the results.
Kindly let me know if this suggestion would have helped you.
I dont know why you have this requirement at the first place. But in order to achieve this, you could go one step back. From where these date properties are fetched? They must be getting from the DB or the user form. I think your requirement is from DB. If that is the case, then write a report def to get it directly from those tables. Use join.