Time different between two time zone

index.php

<?php 
		
		 $db_time = '2017-09-21 12:00:00 PM';
		 $db_timezone = 'Asia/Kolkata';
		 $user_timezone = 'America/New_York';
		 
		 date_default_timezone_set($db_timezone);  //Change default timezone to old timezone within this function only.
			$originalTime = new DateTime($db_time);
			$originalTime->setTimeZone(new DateTimeZone($user_timezone)); //Convert to desired TimeZone.
			date_default_timezone_set($user_timezone) ; //Reset default TimeZone according to your global settings.
			$LATime = $originalTime->format('Y-m-d h:i:s A'); //Return converted TimeZone.
			
			$datetime1 = new DateTime();
			$datetime2 = new DateTime($LATime); 
			$interval = $datetime1->diff($datetime2);
			
			$year = $interval->format('%y years');
			$month = $interval->format('%m months');
			$day = $interval->format('%a days'); 
			$hour = $interval->format('%h hours'); 
			$minute = $interval->format('%i minutes'); 
			$seconds = $interval->format('%s seconds');
			$time_different = '';
			if($year > 0){
			$time_different .= $year. '   ';
			}  if($month > 0){
			$time_different .= $month. '   ';
			}  if($day > 0){
				$time_different .= $day. '   ';
			}  if($hour > 0){
				$time_different .= $hour. '   ';
			}  if($minute > 0){
				$time_different .= $minute. '   ';
			}else{
				$time_different .= $seconds. '  ';
			}
		 echo $time_different. '  ago';
		 
		 
 ?>