That is today–09/09/09.
Apparently, as stated in Yahoo! News, almost everyone has set some special plans for today. This is because the next instance of calendrical digit repetitions will happen in the next century (2101) or in next millenium (3001). Obviously, with the modern human lifespan, there is a small chance for individuals to reach those years.
The Yahoo! article also said that numerologists relate the number nine to “forgiveness, compassion and success, as well as arrogance and self-righteousness.” Asian nationalities like the the Chinese and Japanese have additional beliefs about the number. The Chinese regard it as a lucky number while the Japanese regard it as otherwise since it has the same sound as the word “suffering” in the Japanese language.
Coincidentally, September 9 is the 252nd day of the year 2009–2+5+2=9.
Personally, I’m ‘gonna mark this day by opening a bank account. It’s weird but that way, I get a concrete recording of this day.
The full article from Yahoo! News can be read here.