title: How to setup an RxJS.Observable.timer() with a due date
body: <p>I have an authentication system here which has several information, including an <code>expires_in</code> property, declared in seconds. This informs when the token generated will be expired and, to handle this I'm using the concept of an <code>RxJS.Observable</code>.</p>
  
  <p>With the <code>expires_in</code> value, I calculate the expiration date generating a <code>Date</code> object, incrementing it's value with the expiration, and getting it's time with <code>getTime()</code>, in milisseconds, and with this I have the due date.</p>
  
  <p>When I declare the <code>RxJS.Observable</code>, I'm doing like this:</p>
  
  <pre><code>// The code is shortened to the relevant part
  
  let obs = Observable.timer(dueVar) // Which is in milisseconds
      .subscribe(
          (x) =&gt; console.log(x),
          (x) =&gt; console.log(x),
          () =&gt; console.log('Expired') // onComplete, right? Only this one matters to me...
      );
  </code></pre>
  
  <p>I've tried to put, where is <code>dueVar</code>, the <code>Date</code> object, but no success at all... The snippet throws the first parameter of the <code>subscribe()</code> function as <code>0 [Number]</code>, and immediately throws <code>Expired</code>, which is the last param.</p>
  
  <p>How can I make this operation? I didn't any relevant explanation for that matter... The second parameter, as I saw on the docs, it's optional, and for call the <code>onNext</code> callback every span time that is declared there. But I need to dispatch this one time only.</p>