Change course start and end dates to date-times

I would love to make a course start at 8:30am in conjunction with the first class meeting and stop at 4:30pm to match our official due date time. Currently the course runs the full day from 12:00am - 11:59pm. This variable would be very helpful for any assignments that are "always available". Right now our students see the 11:59pm time for these assignments and use every last second of that time when they should really be submitting those assignments by 4:30pm of that final class day. I can manually enter a stop time for each assignment but this is VERY time consuming when I have 10+ course instances, each with 10+ tests to  manually enter every semester.