Calculate the number of days, hours, minutes and second between two dates

Hi there,
I am trying to analyse some tasks and how long they take in each instance. I need to know how many days, hours, minutes and seconds occurred between two dates. The difficulty i'm facing is that the range is larger than 30 days.

Plus I then sort them and they sort by numerical number not by number of days.

Please help! I'm sure this is relatively easy for the super users on here!

Cheers, Trelacmv