This is controlled on the "Schedule" settings page in the settings section. You also can get there using the "Schedule Settings" button on the Schedule Overview page.
There are "Opening length" and "Closing length" fields. If you put a time period in either or both of those fields, it will be used for your schedule.
Note: The automatically generated schedule does not account for time between stations. So, any "between" time must be included in the previous session. For example, if you had a 15 minute opening session, and allow 5 minutes before the first rotation station, you would enter a total of 20 minutes for the "Opening length."
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