Yeah, that functions in my top twenty used. I'm guessing you'll want some sort of readable format for them, so just tack date() on there, and you should be good to go...
$blar = date("m/d/Y", strtotime("Thursday"));
$blar1 = date("m/d/Y", strtotime("Thursday +7 day"));
$blar2 = date("m/d/Y", strtotime("Thursday +14 day"));
$blar3 = date("m/d/Y", strtotime("Thursday +21 day"));