title: how do I set an existing NSDate's time?
body: <p>how do I set an existing <code>NSDate</code>'s time?</p>
  
  <p>That is I have a date (say current date/time), but then want to set this to a specific time (e.g. 11.23am) say.  What is the quickest way to do this in objective C?</p>
  
  <p>I'm looking at <code>NSCalendar</code> and see methods such as <code>dateByAddingComponents:toDate:options:</code>, and <code>dateFromComponents:</code>, but these don't seem to quite hit the mark for what I need here. For example:</p>
  
  <ol>
  <li><code>dateFromComponents:</code> - I would have to work out all components for this to work which seems like overkill</li>
  <li><code>dateByAddingComponents:toDate:options:</code> - I don't want to ADD in my case but rather "set" the time.</li>
  </ol>