Change a student's enrollment date for a group course.

Regardless of the start date of a course, a student's class attendance can only be entered from his or her course registration date onward.

To change a student's enrollment day for a group course, navigate to Didactics → Group Courses and click on the icon "Students enrolled" on the row of the course in question.
From the next screen, click the edit icon on the row of the student in question.

Then edit the Ddate of start of attendance to the course and click the Edit Subscription to save the operation.