Be sure to check all semester deadlines carefully--I've highlighted a few here:
January 19: Last day to drop without a W
January 26: Last day to apply for Spring graduation
March 2: Last day to change your grade option (remember--all major and minor classes must be taken for a grade)
March 5: Summer 2018 registration begins
March 18-25: Spring Break
March 26: Priority registration for Fall 2018 begins
April 6: Last day to Withdraw from a course
More details at: https://registrar.unl.edu/calendars/AcademicCalendar2017-2018.pdf