You could easily find the latest recycle time by using this powershell snippet:
(Get-Process -Id <ProcessId>).StartTime
Therefore find the process id of your web application in task manager.
First add the following columns via Tools > Select columns… : select PID and Command Line.
Look for any w3wp.exe process and find your application by examining the command-line (application pool name is part of it) and note down its PID.
Then run the powershell script to find the latest recycle time:
Hope this helps