before 6/30/17 16:48:57

$date_query = array(
	array(
		'year'          => 2017,
		'month'         => 6,
		'day'           => 30,
		'hour'          => 16,
		'minute'        => 48,
		'second'        => 57,
		'compare'       => '<',
		'column'        => 'post_date',
	),
);