calculate difference between two dates in scoped application

In my NON scoped app i used gs.dateDiff to get difference between two dates and it worked perfectly.

I am now in a scoped app and cannot use gs.dateDiff.

says to use GlideDateTime.subtract(d1, d2);

that returns a duration object of the form: 2 Days 23 Hours

How do i convert the duration object to seconds?