這是在 programming 版裡看到的：

摘自 Expert C Programming - Deep C Secrets中的一段

Like the Potrzebie system, the joke about programmers' confusion over
Halloween and Christmas Day depends on inside knowledge of numbering systems.
The reason that programmers can't tell Halloween from Christmas Day is
because 31 in octal (base eight) equals 25 in decimal (base ten). More
succinctly, OCT 31 equals DEC 25!

When I wrote to Professor Knuth asking his permission to tell the story, and
including a draft copy of the chapter, he not only agreed, he marked numerous
proofreading improvements on the text, and pointed out that programmers can't
distinguish NOV 27 from the other two dates, either

來源: http://my.safaribooksonline.com/0131774298/ch08

附註：八進位 31 = 九進位 27 = 十進位 25