How to get months and years from deadline date.
var deadline = '12 28 2016 18:40:18 GMT-0400';
var t = Date.parse(endtime) - Date.parse(new Date());
var seconds = Math.floor( (t/1000) % 60 );
var minutes = Math.floor( (t/1000/60) % 60 );
var hours = Math.floor( (t/(1000*60*60)) % 24 );
var days = Math.floor( t/(1000*60*60*24) );
var months = // ?
var years = // ?