I am a little crazy for birthdays-they're a big deal and I believe they should all be celebrated. I have gained some slight level of maturity to recognize that we do not force others to make a big deal of their birthdays, but this Friday is MY birthday, so I can be as obnoxious as I like.
Really, I think we should get more than a day to celebrate. Especially if it is a milestone birthday. Or if your birthday is in the middle of the week, or on a day when you have lots of meetings.
It should be at least a whole weekend. But a whole week sounds even better.
Some of the days happen before the actual anniversary of birth--a time to be mindful of the 'lasts' and to reflect on the year. (Sort of like all the glossy year end articles and top 40 specials...) And then the big day! After, a few more days to extend the celebration to build a strong base of awesome to start the next year of one's life. (And some naps to keep rested.)