title: Is there a way to access a Date as milliseconds since epoch (Date.getTime()) in mongodb aggregation pipeline
body: <p>Mongodb provides lots of '<code>Date Aggregation Operators</code>' such as <code>$dayOfYear</code>, <code>$dayOf Month</code>, and <code>$millisecond</code>. The <code>$millisecond</code> function just returns the milliseconds of the time stamp with a range of 0-999.</p>
  
  <p>Is there a way to access a <code>Date</code> object as milliseconds since epoch in aggregation pipeline?</p>
  
  <p>Thanks,</p>
  
  <p>Nathan</p>