Create a short code in wordpress

function my_shortcode()
{
 //buffering
 //Object Start
 ob_start();
 
 date_default_timezone_set('asia/kolkata');
 
 //echo date('H:i:s');
 
 echo '<div id="mytime"></div>';
 
 // object get contents
 $output_string = ob_get_contents();
 // clean object
 ob_end_clean();
 return $output_string;
 
}
add_shortcode("clock","my_shortcode");