By default, the buttons to register for classes in MySanDiego will default to the latest semester you can register. If you'd like to change your registration for an earlier semester, open the Add/Drop Classes screen and click on RETURN TO MENU at the top of the screen as seen here:
Next please click on Select Term:
Here you can select the term you wish to register for from the drop down menu and click Submit:
Next click on Add or Drop Classes and you will be back to the page you were at before but on the term you wanted.