Copy from "added to library" to "access date"

I have a large number of magazine records where I have not included the “access date” of an electronic copy. My solution is to bulk copy the date from the “added to library” field into the “access date” field. However, although I can see the “added to library” field in my records and can search on it, I cannot see it in the drop down menu in the Tools - change/move/copy fields menu. 

Am I missing something?

Help please

Unfortunately, the Endnote software developers made the “added to library” field inaccessible to users so users cannot copy the data to another field.

But you can request that they add that sort of access as a “copy” field, like I did for the record number?  (suggestions forum, I guess).