Sign off days are Tuesdays and Thursdays at 2:23 PM. The UPS truck picks up the shipping pallets at 2:45 PM. It takes 4 minutes to pack the guitar in a shipping box, another 2 to verify the shipping label, and 7 minutes to transport the guitar from packaging to the loading dock. Then five minutes to wrap the pallet for shipping. That's 18 minutes total, so if your guitar is signed off in the first four minutes, it will make the UPS shipment that day.
But, if it's Thursday, there's a complication. Thursday is Shawn's cheat day, and he goes to the vending machine for a pack of Ho-Ho's. Being a creature of habit, he gets his Ho-Ho's at 2:25 PM unless he's interrupted. If by chance he's running late, he's irritable and slightly less than charitable and tends to forget common courtesy and he will generally cut in front of the transfer cart full of guitars. The problem is, he is immediately wracked with guilt, and always - ALWAYS - stops whoever is pulling the cart to apologize. That delays the cart by five minutes, meaning your guitar misses shipping out that day.
So, send Shawn a box of Ho-Hos. That'll get you your guitar early.