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 14: May 16
End of drop/add for classes beginning June 4: June 6
End of drop/add for classes beginning June 18: June 20
End of drop/add for classes beginning July 9: July 11
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.