Many people are getting married today. The number nine in Cantonese is pronounced "kau", which is a homophone for part of the phrase "cheong cheong kau kau", which means "forever". So today is an auspicious day for getting married because your marriage is supposed to last forever!
On the other hand, some people are avoiding this day because 999 is the emergency call number!
It all depends on whether you're a half-cup full or half-cup empty person.