Convert One Timezone to Another Timezone in PHP

Sometimes we need to convert time from one timezone to another timezone for some challenging scenarios. Change from one timezone to another timezone in PHP.

$date = new DateTime("2012-07-05 16:43:21", new DateTimeZone('Asia/Kolkata'));
date_default_timezone_set('America/New_York');
echo date("Y-m-d h:iA", $date->format('U'));