The release date doesn't capture the actual start date in asynchronous courses where a student can start taking the course whenever they choose. All of our courses are like that since they are provided free to the public (365/24/7) but for reporting purposes I need to track the number of people who started or "enrolled" in a course each month. Since ATutor does not consider these types of students, I added an enroll_date field to the AT_course_enrollment table in the database and modified the enroll.php file to capture and store the information. Fortunately, that is a simple fix but I wish it were an ATutor "feature".
I think the end date can be determined from the last_accessed field in the AT_member_track table. However, I also think before the data is captured by ATutor, a student must be enrolled in the course and member tracking has to be enabled by adding My Tracker to the student tools.