how to get value of datepicker to convert to timestamp using angularjs

<div class="row">
	  <div class="form-group"> 
	   <div class="input-group">
		<span class="input-group-addon" id="basic-addon2">Start Date
		</span>
		<input type="text" id="datepicker1" class="form-control"/>
		<span class="input-group-addon">
		 <span class="glyphicon glyphicon-calendar">
		 </span>
		</span>
	   </div>
	  </div>
	 </div>