I'm not sure how this fits into your OOP code, but here is how I handle date checking:
// Some date variable examples...
$today_now = strtotime(date("n/j/Y", mktime()));
$friday = strtotime("friday");
$tuesday = strtotime("tuesday");
$next_tuesday = strtotime("next tuesday");
// You may want to set some times in the following examples...
$tomorrow = mktime(0, 0, 0, date('m'), date('d') + 1, date('Y'));
$last_sunday = mktime(0, 0, 0, date('m'), date('d') - date('w'), date('Y'));
$next_sunday = mktime(0, 0, 0, date('m'), date('d') + date('w'), date('Y'));
// Then you may just need a few more if statements...
if(time() > $friday && time() < $tuesday)
$delivery_day = $next_tuesday;
else
$delivery_day = $tomorrow;
Hope that helps!