title: TypeError: formats.dateTimeString.toISOString is not a function
body: <p>I'm new to TypeScript and AngularJS, and I'm trying to convert a date from my API that is something like:</p>
  
  <pre><code>"8/22/2015"
  </code></pre>
  
  <p>...to an ISO Date.  The date is properly deserialized into a TypeScript property of type <code>Date</code>.  However, when I try the following command (in typescript, and <code>this.dateDisplay</code> is of type string)</p>
  
  <pre><code>this.dateDisplay = formats.dateTimeValue.toISOString();
  </code></pre>
  
  <p>I get the error:</p>
  
  <blockquote>
    <p>TypeError: formats.dateTimeValue.toISOString is not a function
        at dataFormatsTests.js:42
        at processQueue (angular.js:14567)
        at angular.js:14583
        at Scope.$get.Scope.$eval (angular.js:15846)
        at Scope.$get.Scope.$digest (angular.js:15657)
        at Scope.$get.Scope.$apply (angular.js:15951)
        at done (angular.js:10364)
        at completeRequest (angular.js:10536)
        at XMLHttpRequest.requestLoaded (angular.js:10477)</p>
  </blockquote>
  
  <p>I've also been to <a href="http://kangax.github.io/compat-table/es5/" rel="noreferrer">this site</a> and it says my browser supports the <code>toISOString</code> function.</p>
  
  <p>So, my questions is: Why doesn't my browser, or angular, or whatever, recognize the <code>toISOString</code> function?</p>