The University requires that each professor set specific policies for class attendance. I believe that college students should be treated as adults.
Adults manage their time, set their priorities, and then accept responsibility for their choices.
Therefore, although I record class attendance and use it as one element of the participation grade, if any, I do not establish any explicit penalties for or limits on absences unless stated otherwise in the syllabus for a particular course. Most students cannot keep up with the material in the courses I teach without coming to class. A student's attendance record will very markedly affect my willingness to help that student outside of class. I normally accept excuses only for participation in university-sponsored activities, illness for which you were examined by a doctor, and death or serious illness in your immediate family. Please be on time.