Haha yeah, I dunno what it is... but easily the last 2-3 things I've ordered that have shipped UPS have had an "updated" delivery date about a day or two after it ships.
I got the same thing. Original date is listed, then updated to be a day earlier. It sure beats the heck out of waking up, running to the computer to see the 3 greatest words on the internet ('Out for Delivery') only to get there and find 'Delivery Exception'.
Someone's gonna have a great weekend!
