Sevenday
Variations on 7/7/7 from the available formats for today's date in Microsoft Word:
7/7/2007
7/7/07
2007-07-07
7.7.2007
7/7/2007 12:24 AM
7/7/2007 12:24:44 AM
Plus, even the week lines up, with it being the 7th day of the week.
It's kind of too bad that they didn't release the 7th and final Harry Potter novel today. Now that would have been really cool...