The default start time is 9:00 AM. The number of working hours available per day can be adjusted in the Human Resources section of the Resources sheet. This then drives the automatic scheduling times.
Entering any time greater than 9:00 AM in a predefined start date will be accepted in the task's start date field. Any time entered before 9:00 AM (e.g. 07:00) will convert back to the default start time (09:00) to ensure correct scheduling.