IFS last used date

I am using the TAATOOl CVTIFS to get a file with objects sitting in selected IFS directories. The file being created has four dates for each object. Created, Changed accesses and last used. When I view the files in Navigator that only shows me created, modified and accesses. These three dates are in the past but the last used date looks like it is always "today". Last used date is today even for files I know have not been used. Does a backup change the last used date on IFS objects? I am looking for files that are older than a set purge date and using the most recent date for all dates associated with the object when doing the test to delete. Is the backup is always updating the last used date I would not want to use that in my test but I would want to use the last used date if something other than backup used the file. I have been using this purge routine for a number of years and it seems like only recently we noticed it was not deleting what it used to. We are on V7.1 with V7.3 coming in October

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