Webinar times are a tricky subject. I have played around with them for over a year now. In my own experience, I have found that Mondays & Wednesdays are the best days to put on a show. For time slots, I shoot for 10am PT/1pm PT. Try to cap your webinars (or at least advertise) at 30 min. Most people do not want to dedicate 1hr towrds a webinar.
A quick side note: Get the event on your prospects calendar early. The earlier you get them to register, the more likely their calendar slot is open. Also, in your registration confirmation email, post an "add to calendar" button. That way, you have physically blocked a slot on their calendar, which will boost your registration-to-attendee conversion rate.
If you have any more questions, feel free to reach out.
-Dex