title: Convert DateTime in millisecond iOS
body: <p>I have the date and time , what i want is the no of milliseconds from the particular date and time</p>
  
  <p>for eg: date is <code>21-04-2015</code>
  and time on the date(21-04-2015) is <code>14:23</code></p>
  
  <p>then the output in milliseconds is <code>1429606437692</code>
   <strong>I want the no of milliseconds from 1970 to todays date up to <code>14:23</code> time</strong>
  how to get this date time in millisecond in iOS?</p>
  
  <p><strong>please help and thanks in advance.</strong></p>