That doesn't work for past HITs correct?Each HIT has an auto approve time, which is the maximum time it could take. That's the information that you need..
You can get it by using these
https://greasyfork.org/scripts/3114-mmmturkeybacon-enhanced-hit-information-capsule-shows-automatic-approval-time/code/mmmturkeybacon Enhanced HIT Information Capsule (Shows Automatic Approval Time).user.js
https://greasyfork.org/scripts/3106-mmmturkeybacon-save-automatic-approval-time/code/mmmturkeybacon Save Automatic Approval Time.user.js