DateTime::createFromFormat("Y-m-d H:i:s", '2014-09-12 00:00:00')
->diff(new DateTime('now'))
->y;

var diff = new Date(new Date - new Date(diff_date)).getFullYear()-1970

var sqlDT = "2014-09-12 00:00:00";
var BD = new Date( sqlDT.replace(' ','T'));
var Now = new Date();
BD.setMinutes( BD.getMinutes() + Now.getTimezoneOffset()); // в UTC

if( BD.getMonth() === Now.getUTCMonth()
  && BD.getDate() === Now.getUTCDate()
) {
  // ура! День рождения!
  var y = Now.getUTCFullYear() - BD.getFullYear(); // сколько полных лет
}

function age_count(date) {
    // now
    var now = new Date();
    now.setMinutes(now.getMinutes() - now.getTimezoneOffset());
    now = now.toISOString().substr(0, 19).replace('T',' ');
    // calculate
    var age = now.substr(0, 4) - date.substr(0, 4);
    if(now.substr(5) < date.substr(5)) --age;
    // output
    return age;
}