How to get 2nd last incident creation date?

Content

i trying to make a report that will show us if a client has made another contact into the RightNow within 7 days of a CHAT session. i can use "LAST(incidents.created,incidents.created) " to find when the last time a customer contected to the RightNow.

challanges :

1- How to get 2nd last incident creation date? also second last incident number's source should be the Live Chat.