The next time someone tries to tell me how much thought Apple puts into UI design, I'm going to rip his head off.
*Yawn*... It's now June 17, I've got my morning coffee, and I'm logging into the iBook. Hello, computer. The only indication of today's date on screen is this nice big friendly day-calendar in the dock, telling me it's Jul 17:

Jul 17, hmm.. Thanks, MacOS. You're a pal... so useful and great. Wait a minute! It's not JULY! Is it? Hmm, guess I was wrong. This computer has NTP from time.apple.com. It wouldn't lie to me. iCal certainly wouldn't lie, I mean, it's only fucking purpose is to track the day for me.
Hmm.. July. Wow. I've got some catching up to do. I guess I'll check my appointments, I'll open this iCal up and...
(*bounce*, *bounce*, *bounce*)... whoa! :

It changed! wtf? Oh, it was June 17 after all. Let's close iCal now (*click*):

Cool! The icon stayed on today's date after I closed it.
Open iCal at Jun 17, 11:59. It changes from Jul 17 to Jun 17 as expected. Wait a few minutes. iCal icon rolls over to Jun 18 as midnight rolls around. Neat. So the rule is that the icon is up to date if you've run iCal at least once. Got it.
WRONG!
Close iCal at Jun 17, 11:59. Wait a few minutes. iCal icon never updates. The correction made the last time iCal was run is just frozen in time. What this means is that you can't even train yourself to look for the default Jul 17. It will just show the last date on which iCal was running. This whole issue wouldn't be so dangerous if iCal's icon were consistently either right or wrong about what day it is, or at least looked correct only when iCal is running (then you could look for the little black "running" indicator under the icon to tell whether to trust the icon or not). But no, when there's no black arrow the icon will be RIGHT, if you've run iCal today, and WRONG if you haven't. Let's think of the iCal icon reading algorithm:
Okay, so your users aren't ready for a two-button mouse, but they'll pick up on this Jul 17 nonsense. Sure.
ATTENTION all idiot Apple UI wizards, and all Mac fanatic fags: DO NOT display false information on screen. If you don't know what the actual date is, don't just pull one out of your ass. I've always fucking hated your queer OSes and you're just giving me reasons to hate you. I shouldn't have to tell you this: I'm just some asshole. Show a closed calendar or obscure the date somehow until you know what day it is. Don't just bullshit me!
Actually, come to think of it, iCal is active even before it is launched. I know because past-due alarm dialogs are sometimes triggered as soon as I log in. Think about that for just a moment. Something is constantly polling iCal for its alarms, and iCal is getting a chance to see what the current date is. Wouldn't THAT be an appropriate time to correct the dock icon? They'd rather have iCal's launch date sitting there as a little user-misleading easter egg. Like anyone cares when Jobs announced your stupid brushed-metal ass. Cute. You make me sick.