- var_dump: documentation ( source)
<?php
$eastern = new \DateTimeZone( 'America/New_York' );
$time = new \DateTime( 'now', $eastern );
$ad_active_time_start = new \DateTime( 'December 18, 2015 9:00am', $eastern );
$ad_active_time_end = new \DateTime( 'December 19, 2015 10:00am', $eastern );
var_dump( $time > $ad_active_time_start );
var_dump( $ad_active_time_end > $ad_active_time_start );
echo $ad_active_time_end - $ad_active_time_start;