title: Mark and check a process if it's completed or not
body: <p>I'm not sure how to write this line.  What I'm looking to do is write one statement that is only done once and upon completion marks itself to not be done again(To avoid a constant loop) for something like a day time and night time.</p>
  
  <p>What I think needs to be written:</p>
  
  <pre><code>    if ([nightTime timeIntervalSinceNow] &lt;= 0 &amp;&amp; "check if already reset or not"){
          // The following process has to be done, but only once
  
          // reset dayTime (for tomorrow)
  
          // stop the current NSTimer
  
          // recreate a new NSTimer for nightTime        
  
     }
  </code></pre>
  
  <p>Can anyone point me in the right direction of what I should use?</p>
  
  <p>Many thanks!</p>