I Don't Know How Old I Am (Or: Proof that I am an Idiot: Pt. XXIII)

I was going to write a long post about my birthday weekend (which was fine, nice and low-key) and all the things I did (ate too much, watched a couple movies, put up some shelves in the bedroom, did NOT go workout) but instead I'll boil it down to the following incidents, which underscore that I DON'T ACTUALLY KNOW HOW OLD I AM (or rather, How easily I can be tricked into thinking I am a particular age when in actuality I am something different.)

(But before I begin the following caveat: I don't really think too often about how old I am. My age doesn't bother me; I don't obsess about it; and at any given time I'd have to stop and think about what my actual age is. Now that we've established these caveats, let's move forward):

• #1. – Yesterday, in the condo: My brother and Kari buy me a birthday cake and the two of them, along with Richard, bring it out to me after dinner and sing "Happy Birthday." I noticed that the cake has two candles for "38." I immediately think this is odd because I'm not 38, I'm 37. So I say, "I think we need to put this cake in the freezer for a year because I'm 37 today, not 38." After a lengthy discussion between the four of us pertaining to my brothers age, the age difference between us, some wizardry I can only describe as “new math” the three of them have me convinced that I am a moron who doesn’t know how to add correctly and figure out his age, and that I am really ONE WHOLE YEAR older than I thought I was. And while I feel I took the news rather well, I was sorta shocked that I’d been going around all this time thinking I was turning 37. How could I be off by a whole year?
• #2. – Yesterday, lying in bed staring at the ceiling: Richard asks me if everything is OK, if it bothers me that I’m 38. I say, “It isn’t the fact that I’m now 38 that bothers me; it is the fact that all day I’d been walking around thinking I was a year younger than I really am. How did this happen?” I think back to my birthday last year -- was I going around saying I was 36 when I was really 37? While I remember it (stalking Robbie Williams on Old Bond St. with my friend Sean, party at my friend Kate's flat in London, lots of Pimm's, a birthday present involving a coffee cup with a photo of a guy at the beach who's shorts disappear when the mug gets hot) details are fuzzy as to what age was discussed.
• #3. – This morning, at work: Talking to my mom on the phone, relaying the story of what an idiot I am because I’m not 37, I’m 38. We both laugh.
• #4. – This morning, at work: My friend Phillip emails me, asking how my birthday went. I reply back saying it was fine, but in typical Will fashion, all day I thought I was 37 when in fact I didn’t realize until the evening that I was actually 38. He replies back with: “Are you smoking?? You were born in 1969 so that makes you 37. You’re 37, not 38.”
• #5. – This morning, at work: I have a complete, though temporary, mental and existential breakdown. “How old am I, God?” I ask myself, “Seriously? How old am I? I ask you because apparently neither I, my brother nor my own mother know.” After some additional calculations it is determined that I am really, truly, seriously 37 years old. I am thinking about getting it tattooed to my palm.

How is it that a reasonably intelligent, successful person can walk around for approximately 13 hours not knowing how old he is?