in the 1st exercise of WP7 lessons the description of the exercise mentions:

"You'll save the world by allowing a mobile user to type in a special sequence of numbers every 108 minutes."

While this is a very interesting exercise, in the solution that follows  there is no example about how to set the timer for every 108 minutes. We just get to practice the "if" statement with resulting text when a button is pressed.  

We indeed have seen how to check the time now and add or deduct units or convert from one format to the other, but not how we could combine the iteration method with time and if statements to create a timed event.  

I feel that same as i got lost there, others might get lost as well.