I heard the news of the tens of thousands of Chinese couples married on the 9th of September 2009. Because the number 9 九 is pronounced as 'jiu' whose sound is the same as the word "long-lasting" 久 in Chinese, many think the date of 9/9/09 is an auspicious day to seal the deal.

久/久/永久 - long lasting forever maybe pronounced as jiǔ jiǔ yǒng jiǔ

Funny story~