Update an ACF Field based on if the date is in the past.

update_acf_date_field.php

function tct_set_new_date() {
	$posts        = get_posts( array('post_type' => 'session', 'posts_per_page' => - 1) );
	$current_date = date( "Y-m-d h:i" );

	foreach($posts as $post) {
		$old_date = get_field( 'date', $post->ID );

		if($old_date < $current_date) {
			$new_date = date( 'Y-m-d h:i', strtotime( '+1 week', strtotime( $old_date ) ) );
			update_field( 'date', $new_date, $post->ID );
		}
	}
}


if(!get_transient( 'tct_date' )) {
	tct_set_new_date();
	set_transient( 'tct_date', 1, 60 );
}