The drop-add period ends at the end of the business day (4:30 p.m.) on the third day of each session.
End of drop/add for classes beginning May 13: May 15
End of drop/add for classes beginning June 3: June 5
End of drop/add for classes beginning June 17: June 19
End of drop/add for classes beginning July 8: July 10
For dynamically-dated classes (those that do not conform to any of the regular summer sessions), the last day to register is the day before the class begins.