General availability for each of the four U.S. time zones is listed below.
U.S. Pacific Time
12pm - 4pm
U.S. Mountain Time
1pm - 5pm
U.S. Central Time
2pm - 6pm
U.S. Eastern Time
3pm - 7pm
Start times are usually at 4pm and 6pm ET.
Sessions are allowed to go over an hour. I generally try to separate start times by at least 2 hours, giving students the option to have at least 90 minutes.