NW is not be able to return the latest date a media has been written to - it 
just knows the last READ or WRITE time (volaccess).
I would modify your command as follows:

  mminfo -q "family=tape,clonetime>=-xdays" -r "volume,clonetime,clretent" -ot 
-xc, > outfile

This will limit the time range and will already sort the result by time. 

Then import the csv file into an Excel sheet and filter the data appropriately.

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