An assignment that I receive before the end of my last scheduled class on the due date will count as being on time.
Except perhaps for the last assignment of a semester, I will accept assignments up to one class day late, with a 20%-30% penalty on those parts that are late. Anything after this does not count. For example, a 100-point assignment that was turned in half on the due date and half at the next class meeting would receive a penalty of half of 20-30%. If it was otherwise completely correct, it would probably get an 87. Late submissions should be turned in by the beginning of class. Late submissions may not be graded as promptly as work turned in on time.
It never hurts to turn in an assignment on the due date, even if it isn't correct. In general the grade that you get will be the better of the grade for the version turned in on time (partial credit with no penalty applied) and the grade for the late version (with the penalty applied). If I return the earlier version on the day that you turn in a later version, please resubmit your original assignment on that day -- I will need it to complete the grading.