Hi: The Patuxent Visitor's Ctr. is open every day of the year except Christmas, from 10 am to 5 pm. Trails are open until 5:30 pm (so I assume that means they don't close the gate on Pawder Mill Rd. until sometime after that!) The Sandy Hills Landfill is open 7 am to 4 or 5 pm (I forget) M-F and from 8 am to noon on Saturday; it is closed Sundays (hence gulling is not so good on Sunday) as well as major holidays. Gail Mackiernan