Right now, my kids are counting down to December 1, when they can open their Lego Advent calendar. Since they will soon enough be counting down to the main event, I went ahead and whipped up this very simple little counter in html to show the C-minus day. I embedded it in my LAN splash page using an iframe, but you could also just put it on the desktop and open it directly. The code is posted on GitHub.
Don't worry about my math. I forced it to 25 days for the screenshot!