I agree. Without a timestamp there is no way for libraries to count the number of deleted patron records in a given time period for reporting purposes.

I think if you have the borrower log turned on in system preferences you can find out the number using the log viewer.

How do you use the log viewer to create a saved report which lets library staff run reports to get counts of deleted borrowers? Many libraries need this information for annual reports.

The log viewer is build on top of the action_log or/and statistics table (not quite sure ther) - was just trying to say that the information is there :)

I agree, there should be a timestamp field on the deletedborrowers table.  I'm willing to bet that the reason there isn't is because there isn't a timestamp on the borrowers table to begin with.  All of the other deleted* tables as well as old_issues and old_reserves have timestamps because their corresponding tables all have timestamps.

That being said, I did read this before I sat down to write this comment and, based on Katrin's comment, I wrote a report that can get a count of deleted borrowers based on the data in the action logs.  It's on the Wiki if anyone needs it (like I did a couple of hours ago when I started poking around in the first place).

The value of the timestamp field in borrowers and deletedborrowers would come from making a report like this possible for libraries that don't have the BorrowersLog system preference turned on.

What about this:

CREATE TABLE `deletedborrowers` ( -- stores data related to the patrons/borrowers you have deleted
[...]
  `updated_on` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, -- time of last change could be useful for synchronization with external systems (among others)

See also bug 10459