The Add deadline, the last day to sign up for a class in SIS, is September 7th. I would advise you against adding a class two-weeks into the semester unless you've been attending that class regularly, or have made some other arrangement with the professor. September 8th is the last day that you can drop non-engineering classes, like Chemistry, Physics, or humanities courses. The Drop deadline for engineering courses isn't until October 14th. I suggest that you put these deadlines in your calendars and be very careful not to miss them! There's no such thing as a ‘late drop.'