Not exactly wizard code, but why not publish it anyway... I googled for an example like this myself but had trouble finding a good match. Maybe it was more a question of finding the right keywords to search for.
I use this code on the Swedish site for the World Usability Day.
function daystogo() {
// my target date is November 14th 2006
$then = mktime(0, 0, 0, 11, 14, 2006);
// calculate difference between now and then
$now = time();
$diff = $then - $now;
// second, minute, hour
$days = round(0.5 + $diff / 60 / 60 / 24);
// make sure we do not return negative zeros
if ($days == -0) $days = 0;
return $days;
}
// somewhere later in the code...
$days = daystogo();
// if ($days > 0) ...