Time windows for route optimizations and start point of time

I would like to know how to use time windows for optimizations API. For ex. I have a route which starts on Monday, 7 A.M. I’d like to have some stop within time range Monday, 8-9 A.M. How to do this? I know you have time windows, but what is a start point when I send the route to optimize? What is timezone for start time’s point?