title: How to check what day of the week it is (i.e. Tues, Fri?) and compare two NSDates?
body: <p>I'm looking two do two things:</p>
  
  <ol>
  <li>Check if a week has gone by (based on the day of the week)</li>
  <li>Check if a day has gone by (based on the date)</li>
  </ol>
  
  <p>I'm not sure what the best way to solve this is, since when comparing two NSDates (one at 1/1/09 at 21:30 and another at 1/2/09 at 00:30) I can't just see if 24 hours has gone by since in this case it hasn't. I can solve this by just getting the date 1/1/09 from the NSDate, but I'm unsure how to do this based on the documentation and google links that I saw. </p>
  
  <p>For the other issue, I don't know how to know what day of the week it is given a date. I'd like to if 1/1/09 is a Tuesday, Monday, etc... Is there any library that let's you calculate this? This obviously needs to take into account leap years and a tons of other stuff... Maybe there's an objective-c library for this?</p>
  
  <p>Thanks for any help!</p>