So, my birthday's coming up. On the 20th, I'll be turning 19. I feel way older than I am. (Probably because I hang out with so many writers who are usually much older than me. Then again, my mother always said I acted 30 when I was 10, so you never know.)
But, all this thinking about birthdates made me wonder if characters deserve birthdays. If you don't plan on throwing them a party, what's the point?
I'm going to wave my "characters are people too" flag here. Because I suck at writing characters. I'm 100% a plot writer. Some of my earlier books, my MCs were cardboard cutouts. (Yet my side characters were fully fleshed out. I think I may need a psychological analysis.) But after a few trial and error books, I realized characters were never going to just "come to me" like my plots did. I had to work on them.
So what do I do? I create the most extensive character interview sheet out there. (If there's one that's more extensive, I don't want to see it. Mine's three pages long.)
I hate starting a new book because it means I have to run my MCs through my interview process. While very helpful, it's also time consuming and incredibly boring. But birthdays are on there! Because I feel it really helps get a grip on who that character is. Especially in an urban setting.
Just think back to elementary/junior high/middle school. Kids in the same classes are all about the same age, so when you're that age, you use the dates of birth to determine who's older than each other. (There was a girl who was born on Feb 4 in my junior high, and because she was born 16 days before me, she was definitely the "older kid." It traumatized me, since being born in february, I was used to being "older" than all the other kids.)
Why should this matter? Because depending on where your character was born in the year, it's going to determine how the other kids in their class see him/her, and how s/he views them.
For example. A friend of mine who was born on Dec 23 was always seen as younger than everyone else. Because when she was turning fourteen, everyone else was turning fifteen. That can frustrate a kid. (Especially when you just turned 17 and all your friends just turned 18 and you can't go to the bars with them for another year.)
In the long run of your urban fantasy, is it really going to matter? Probably not. But I like to think if you're ever in a situation where a reader, or a critic, is asking you questions, those small details show you've really thought about your book, and you know what you're talking about.