title: Java: how to use Date / Calendar
body: <p>I'm making a small project for my university which is supposed to enroll students into different courses. I do have one issue though, each course has start/end enrollment day. How can I now use <code>Date/Calendar</code> to avoid having to make my own method. I will need two though, one is <code>setDates()</code>, used to set start and end dates for enrollment, and second is <code>isOpen()</code>, which will return error if a student tries to enroll too early or too late. (Assuming the moment of applying is the moment the program is run, so basically "now")  </p>