I think this conclusively proves that Marge is a Culture agent, and held Bart in stasis in her womb for several years before allowing his embryo to fully develop.
The SNPP, as usual, has a befuddling amount of information - every possible source, all of them confusing. But hey, they try.
Homer’s b-day is given as 5/10/55. Marge is definitely not much younger than him; her age is listed as “within one year” of his. I thought I remember him being a grade ahead of her in “I Married Marge,” but I may be wrong. It also says they were married in 1980. They don’t cite what episode they get each tidbit from; the show’s chronology is often (intentionally) contradictory. After all, none of them have aged since 1989, but the country has gone through three different presidents and all that. Basically, they don’t give a rat’s ass about temporal consistency. Ditto the “where is Springfield” stuff.
These minor blunders are inevitable with any long-running series with a multitude of writers and producers.
39 isn’t a bad guess, and it’s easy to just change it back in the next ep, so I doubt anybody made a big deal out of it.
[quote]
thought I remember him being a grade ahead of her in “I Married Marge,” but I may be wrong.
[quote]
They were both seniors.
Well, if that’s not the definitive source on the question, I don’t know what is.
Although “blunder” implies they try to get it right, which I don’t think is the case. 
I honestly just don’t think they care - they’re not getting paid to obsess over this stuff, and we do it for free.
By the way, Homer J. Simpson, you never explained your OP. Why is it impossible (or hard to believe, even) that Homer was 29 when Bart was born?
Because, Marley, as has been stated many times, Bart was concieved out of wedlock, and Homer and Marge were married shortly after they graduated high school.
That sounds like a Special Circumstance to me.
Exactly.
In fact, in the more recent series, they seem to have finally wised up, and dropped any time or historical references - which is a smart move.
If you’ll remember the flashback to Bart going through the “Terrible Twos”, the music put it at about 1983-84. This, of course, would make Bart about twenty-two years of age now.
It’s a cartoon, dammit. And a damned good one. Enjoy it.
If Homer was born in '55 that would sort of conflict with the Woodstock flashback scene from this episode. In the flashback Homer appears 8-10 instead of 14 as suggested by his birth date.
Just another small inconsistency I guess.
He always struck me as someone in their late 40’s.
Wow a 15 year gap in replies on this thread.
[Moderating]
Hello, chunder, and welcome to the Straight Dope. Yes, that is indeed a long gap in replies. While we don’t have a hard and fast rule against reviving old threads, we request that it only be done to add substantive new information, as it’s difficult to carry on a meaningful conversation over the course of decades. As such, I’m closing this.