title: How to declare constants
body: <p>I'm steadily getting the hang of Objective-C, but am still very much a beginner and have a beginner-level question hopefully someone could shed some light on:  </p>
  
  <p>If I have a very simple project and want to set a constant that I'll use throughout—say, a NSDictionary with keys being month names and values being days in that month—how is this done?  (I.e., what command form and where to put it?)</p>
  
  <p>NOTE:  <em>If this example is already possible using built-in functions, perhaps we could just pretend it isn't for the purposes of this question ;)</em></p>