Trouble saving and loading user defaults Date/ Int for Timer.

I am trying to update a timer when the app is closed and then re opened, I know its a case of saving the time its closed, then calculating the difference between time closed and opened before adding it to the time count prior to it been closed, I have implemented the above code and for all the reviewing in the world I cant seem to figure out the issue.

Any help would be massively appreciated.

I have reviewed other similar problems but as of yet haven't found the solution, from my code I cant see where I sam going wrong .

Thanks again!

Josh