I will be in Athens on 9/20 and 9/21(Sunday and Monday). I intend to see the Acropolis and the surrounding sites on Sunday, the spend most of 9/21 (Monday) at the National Archeological Museum. But, I keep seeing some info that says the Museum is closed on Mondays, other info that it is open 12:30 to 7:00 or 1:00 to 7:30. I really need accurate info, so I don't mess up and miss seeing this Museum. Is it open on Mondays, or not? Thank you for your help!