title: Get first day in a month from NSCalendar
body: <p>I have this subset of a method that needs to get day one of the current month.</p>
  
  <pre><code>NSDate *today = [NSDate date];  // returns correctly 28 february 2013
  NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
  NSDateComponents *components = [[NSDateComponents alloc] init];
  components.day = 1;
  NSDate *dayOneInCurrentMonth = [gregorian dateByAddingComponents:components toDate:today options:0];
  </code></pre>
  
  <p><code>dayOneInCurrentMonth</code> then prints out <code>2013-03-01 09:53:49 +0000</code>, the first day of the next month.</p>
  
  <p>How do I get day one of the current month?</p>