Allow me to spell this out for you in the most explicit terms. Any time you miss a class, be it excusable or inexcusable, you should explain your absence in an e-mail with the subject line Absence. Without such an e-mail, I will consider any absence inexcusable. Do not interpret this to mean that you have two free skip days. You are still responsible for the work you miss, and you will receive a grade of zero for each assignment you miss because of an inexcusable absence.
Many students miss the first day or two of the semester because they registered late.
These absences are not excusable. I strongly discourage missing class on days when papers are due. If your absence is not excusable, then you will receive a grade of zero on the assignment. Tardiness will also hurt your class performance. You disturb a class when you come in late.