Try using UTC to calculate the time spent or difference in time .
Method 1 : Set eVar and event with current time when user lands on the page and use it as campaign stacking.
e.g time1>time2>time3
as user proceed with the pages it will keep appending the current time, later you can find the difference .
Method 2 : Create a universal link tracking which will do the UTC difference and record in a eVar and event whenever user choses to navigate to other page.
This can be triggered on clicks.
~Dev aka-Devil@Sitecat