What kind of database to use?

So I’m making a mobile web application that allows one to schedule a meeting. Ideally the business would have a console in which they would be able to blot out certain times when they are busy so that people cannot make a meeting during these times. How should I go about doing this? MySQL would work. The console could tie into the database and have available times. Would XML be better for this? Tell me what you think.

I think you are in over your head or reinventing the wheel, scheduling is a very difficult problem. People still whine at me daily about edge cases that Exchange can’t handle, and that is a few billion dollars worth of development at this point.

So should I just drop it and leave the blottingouttimes bit out of it?