If the UCI had stood by and waited till Wednesday for Landis to appeal for the B sample to be tested the result would not be known for several weeks as the laboratory shuts for the holidays at week's end.
Presumably that's the deadline. Story started hitting the wires here last Wed night / Thurs AM? Thurs-Wed would be 5 business days. One might also note that the deadline indicates when Landis/Phonak were notified, so it's obvious that the leaker(s) wasted no more than a few nano-seconds before they picked up the phone...