My family has this tradition of celebrating people's birthdays the Sunday before. I think several factors went into this:
1) When we were small Dad sometimes wouldn't get back from work until 7 or 8. When you have a 9 o'clock bedtime, that doesn't leave much time for a party.
2) Mom has enough to do during the week without having to make a cake and etc. on top of it. Sundays, being more or less days of rest even back in the days when we were more lax with the whole Catholicism thing, allow the opportunity for such special endeavors.
3) When we were in public school, we couldn't very well take the day off in honor of our birthdays. After we started homeschooling, it caused too much insubordination in the ranks to have one kid take a day off school while the other toiled away. (Added complication: My sister's birthday is in the summer, when we often didn't have school anyway, while mine is in the fall.) So now we get Sundays off, which means Mom still gets the entire week's worth of chores out of us except washing the dishes Sunday evening.
In short, there are lots of reasons why we do birthdays on Sundays. It occured to me this morning, however, that I will have a harder time following this tradition when I establish a family of my own.
You see, the Sunday before Scott's birthday is almost always Father's Day. (The only exception would be years when Father's Day was the 15th, in which case Scott's birthday would fall on the Sunday following.) And that would just be lame, to have Father's Day get subsumed under his birthday. He had no control over the fact that he was born within 7 days of it (now I'm curious what day of the week Scott was born on), just as I had no control over the fact that I was born 6 days before Thanksgiving. (Some years I get lucky and it's a whole 11 days before. When I turned 18 it was only 5 days.) The difference here is that extended family expect you to show up for turkey and such even if you've just had cake a few days before, whereas nobody but you really cares if you celebrate Father's Day or not. Still, I think it'd be pretty lame not to.
Of course, we could be super-Catholic types and celebrate it on St. Joseph's feast day, which is conveniently located in March. (Get a break from Lent and avoid birthday conflicts! Unless you go and have a kid born March 19th. Then you're just stuck.)
(It occured to me as I wrote this post that there also seems to be a "problem" in big families of birthdays coming kind of clumped together. If you have 12 kids, it is highly unlikely that they are all going to be born in different months. You might have 5 all in May. In which case having the party the Sunday before the birthday would likely mean lumping at least two kids together. Necessary, sometimes, especially if you have twins or non-twin birthdays back-to-back or something, but still to be avoided if possible. So I might have to rethink the Sunday tradition regardless.)
UPDATED to add: According to this page, June 22, 1989 was a Thursday. You now have a completely useless piece of trivia to file away in your brain. (Unless you are Scott's parents,--Hello!-- in which case you probably already knew this.)