title: Parse/MongoDB using dates in ISO format as keys in dictionary
body: <p>I have a dictionary of timestamps where I want the <code>date in ISO Format</code> to be the <code>key</code> and a <code>string of what occured on the date</code> to be the <code>value</code>. </p>
  
  <p>ex. <code>timestamps[date.toISOString()] = "SignedUp"</code></p>
  
  <p>The ISO String by default is <code>yyyy-MM-ddTHH:mm:ss.AZ</code>, so I'm getting this issue:</p>
  
  <p><code>[Error]: Nested keys should not contain the '$' or '.' characters</code></p>
  
  <p>Is there a way I can use the ISO Date String without getting this issue? Our backend stores dates using this format for everything so I'd prefer if it could stay that way. Thanks in advance!</p>