How do i get the date of the 3rd monday of the current month.
By looking at a calendar?
Oh, you mean using PHP, don't you? Have you looked at the date/time functions? strtotime()? Did you look at the User notes?
$thirdMonday = strtotime("+2 week Monday", strtotime("first ".date("F"))) + 43200;
Always looking for a better way to do things.