Needfest Special mainly due to laziness and a lack of good ideas. But wouldn't you know it, much to my surprise (chagrin), our good friend Mr. Klein over at Greyhawk Adventures 576CY called me out on a good subject I haven't covered before. It's short notice so I apologize for the lack of annotations. Read the comic, then read the commentary below. Enjoy!
The relevant facts you need to know: In the World of Greyhawk, there are twelve months each with 28 days (and four week long 'fests' every three months) totalling 364 days per calendar year. There are seven days in a week, starting with Starday, then followed by Sunday, Moonday, Godsday, Waterday, Earthday and Freeday. What all this means is, unlike our Gregorian calendar with its varied length of months, days of the month in Greyhawk always fall on the same week. Thus it is impossible to have the analagous "Freeday the 13th" since it would always be Earthday the 13th. Tsk!
This isn't to say people of the Flanaess aren't still superstitious of the number 13. The number can still hold plenty of dubious connotations if applied in the right fashion. Especially if you're a worshiper of this guy.