This article refers to the "English" calendar.
Of course, it should refer to the "American" calendar.
In England, like in most of the rest of Europe, the week is deemed to start on Monday, not Sunday. Thursday is, therefore, the fourth day of the week, not the fifth.
To modify the script to cater for this, instead of simply adding 7 to the result before the modulus operation, it would be better to add 14 and then SUBTRACT the "standard" index number of the first day of the week in your locale. (This should cater for the zero problem pointed out in an earlier post.)
(looks a lot more complex expressed generally than specifically)
Similarly, the date format is different.
Today in America is 02/19/2010, in England it's 19/02/2010.
As a computer geek I actually prefer the Japanese method of writing dates (like 2010/02/19), as this can very easily be used as a (part of a) file name, eg SQLBackup_20100219.BAK - Now if you have many files in a single directory/folder you can sort by name and they're nicely in date order too :-)
BTW - I think that it is a very good article, just nit-picking American/British differences. After all, the Brits walk on the pavement, the Americans drive on it... :-)