Whose timezone will the lessons take place in?

There is no specific time zone, but rather lessons are converted to your own time zone and the tutors time zone respectively. This means that when you book a lesson from your time zone the system converts it to the tutors time zone, hence it can be 7 pm at your time zone and 8 am at your tutors time zone, so just book available time slots in the teachers slot that's available in your time zone.