Do Wisconsites account for 75% of U.S. brandy consumption?
21-May-1976
Some of the columns get up-dated, on a pretty ad hoc basis, but the original date isn’t changed. It’s about as simple as that.
So are you stating that as fact? Sounds like you just picked one of the obvious guesses.
Other obvious guesses: The wrong date was ascribed in the link. Or Cecil just decided to answer an old letter a dozen years later, when the facts were more in line with his answer.
Or there is a conspiracy of hackers putting these conundrums up to mock the Perfect Master.
But, since we are letting guesses substitute for knowledge, I guess we’ll never know. 
We’ve mentioned this before, but here goes again.
When a classic column is posted, the Staff Person who does the work sometimes looks around a bit to see if there’s any obvious updating. If there is, such changes are sometimes made. The updating process is somewhat ad hoc, and depends a lot upon the Staff Person’s mood at the moment, hunger pains, weather headaches, allergies, etc. etc. Usually, the updating is only small bits here and there – there is no systematic effort to re-substantiate and update the entire column. That would be way more work than the READER is willing to pay for.
Some of us regular dopers do unofficial updating too 
So, According to Pliny, no, I was not guessing. although I am grateful for the gratuitous sarcasm.
C K Dexter Haven - So, do they ever get updated because of comments posted here?
A lot of actual errors are reported, but I’ve gone back to a few of the columns later and no changes had been made.
I think Cecil will only reply to update letters that are sent directly to him, just as he’s never answered a question that’s appeared on GQ.
Why is that?
It’s especially strange since every column has a link here with the title “Comment on this answer”. So you would think that was the proper way to point out errors.
In a thread I had started, Fatima message is secret no more, Cecil himself posted “You will forgive me. I was pressed for time, and figured someone would dig up the link for me. Behold, it has come to pass. The column has been updated. Thanks to all for your help.” The column is located at What happened to the secret message of Fatima? – Cecil’s update begins with the section titled “BUT SERIOUSLY . . .”
Not so. Several times a year Cecil addresses in the column a point raised in the Comments on Cecil’s Columns forum. For example, Remembering the Alamo (and the death of Davy Crockett) addressed the point raised in the thread Alamo Diary Forged? Was Cecil Adams fooled? - Jose Enrique de la Pena
Cecil doesn’t post much in GQ, but perhaps a few times a year he picks a question from GQ to answer in his column. For example, What caused the massive 1908 explosion in Tunguska, Siberia? from the GQ thread The Tungus Event
He most often reads Comments on Cecil’s Column, he likes to read the kudos and compliments, the gushier the better. And occasionally, some cause corrections. However, only Cecil would dare correct his own columns, none of the lesser mortals on Staff would ever consider such a thing.
Comments on Staff Reports does produce some revisions in the original reports, from time to time. Those changes are made when the original author agrees with them, and sometimes that doesn’t happen for a variety of reasons – like the original author is no longer involved with Straight Dope, or was last seen hiking through the Amazon rainforest, or whatever.