Why? Because in many cultures seven is regarded as a lucky number, so July 7, 2007 -- 7/7/07 -- is lucky times three, if you believe in that sort of thing.
It has been pointed out that an even luckier date gave cause for celebration exactly 30 years ago -- 7/7/77. Archived news stories from the time show that folks went wedding-happy then, too -- although, curiously enough, the same thing happened again on 8/8/88 and 9/9/99.
Digging back even further, I looked for evidence that lucky-seven mania took hold 100 years ago on July 7, 1907. Turns out it did not -- which is puzzling. Are we more superstitious today than we were a century ago?
Speaking of being superstitious, those who are so inclined will probably want to stay home behind locked doors the following weekend -- it's Friday the 13th.
Poll: Do you believe in lucky numbers? 1) Oh, yes! 2) No way. 3) Not sure.
More About 07-07-07:
• Hitting the Jackpot with a 7-7-07 Wedding - About.com
• Couples Lining Up for the Seventh-Year Hitch - Los Angeles Times
• The Number of the Feast - The Economist
• Luck Number Seven - The Telegraph
• 77 Things You Need to Know About 07 - The Independent