Why is October 13 known as “International Skeptics' Day”?
Mark Honeychurch - 27th October 2026
In David Almandsmith’s article in this issue of the newsletter, he questioned why October the 13th is International Skeptics Day, and announced that International Skeptics Day 2027 (October the 13th again) will be the date for the next event. Now, I have strong feelings about this (something that won’t be much of a surprise for those of you who know me well!).
The first two Global Skeptics events were hosted for 24 hours from Friday evening NZ time, with different skeptics groups joining and hosting as we reached Friday evening in their time zone. This had the benefit of allowing Kiwis, Aussies and the residents of other countries close to, and West of, the International Date Line to join the 24 hour event not just on Friday evening, but also through the day on Saturday. The most recent event, being hosted from Tuesday evening to Wednesday evening, didn’t lend itself to being able to drop in like this - as most of us had to work during the day on Wednesday. It seems to me that hosting the event for 24 hours from Friday evening, or even better from Saturday evening NZ time (which would be from Friday evening to Saturday evening in the US), would make the event accessible to the most people possible. New Zealanders could dial in at any point from Saturday evening to Sunday evening, and anyone between us here in NZ and the West Coast of the US would still find the entire event occurring during their weekend.
So, with this in mind, and considering David’s unanswered question of why October the 13th is considered International Skeptics Day, I set off to find out as much as I could. As a Good Skeptic™, I’d already taken the time to look this up a couple of months ago, when I first heard that this year’s Global Skeptics in the Pub was on Tuesday the 13th of October. Back then I’d basically just read Google AI’s summary, which had told me that both October the 13th and January the 13th each year were considered International Skeptics’ Day, but that traditionally the date changes every year. However that’s just not good enough for an article in our journal - I needed to be able to cite my sources.
From what I could find online, International Skeptics’ Day was created by Adrienne Koopersmith, a prolific inventor of “holidates” - her term for unofficial days of celebration, which she describes as “feel good, anti-gloom events to make our WORLD a better, sweeter and kinder place in which to live”.
According to a blog post Adrienne wrote in 2019, she had by that time invented over 2,500 dates, including Little Black Dress Day, Pay a Compliment Day, Lost Penny Day and International Skeptics’ Day. Although there are no more details about International Skeptics’ Day on her blog, there is an article on Checkiday, a website dedicated to these quirky days, that claims that:
Created in 1996 by Adrienne Sioux Koopersmith, who has called herself “America’s Premier Eventologist,” Skeptics Day International is a floating holiday that takes place on every Friday the 13th as well as on Election Day each November. It is held on each Friday the 13th because those days are associated with skepticism and superstition, and it is held on Election Day since so many voters are skeptical as to who they should vote for. When the holiday was created, it was called International Skeptics’ Day, and it was just held on each Friday the 13th, not on Election Day. It is a day to be skeptical, to be superstitious, and to question things.
I couldn’t find anything on the Checkiday website describing where they sourced their list of holidays from, but I did find some general information on their about page about their process:
Checkiday (chek-ih-day, a mashup of “Check” and “Holiday”) was founded on February 12th, 2011 by Seth Westphal. Although the internet contained a fair amount of holiday lists at the time, none of them seemed complete, were able to show you just today’s holidays, told you anything about each holiday, or were easily searchable. Checkiday was created with the goal to be the world’s most complete holiday listing which would automatically update to show you today’s holidays.
The closest I could find was a claim from Google AI that Checkiday uses the Chase’s Calendar of Events, an annual publication that, since 1957, has been listing important and unusual dates - mostly related to the USA. So off I went to see what I could find in Chase’s records. As the book is a for-profit resource, there’s no dedicated website holding a searchable list of all the dates they publish, but thankfully the Internet Archive (at archive.org) has a back catalog of scanned issues, going back to the 1980s.
The earliest copies of the book the Internet Archive had, from 1986 and 1989, had no mention of International Skeptics’ Day. This wasn’t overly surprising, given that the text I was trying to verify claimed the event was invented in 1996. The early 90s are missing from the archive, but a copy of the 1996 edition has been scanned. For 1997 there was a Sports Calendar special, as well as the standard edition. There was also a copy of the 1998 edition, with “Free CD-ROM Enclosed”.
Sadly there was no mention of International Skeptics’ Day, or of “skeptics”, “skeptic” or “skepticism” in the 1996 issue. This wasn’t overly surprising, as presumably the calendar had been sourced and compiled back in 1995 - before the event had been coined. The 1997 Sports edition had nothing of use either, which was unsurprising given that it focused on sporting events - as the Welcome page made clear:
Welcome to the first edition of Chase’s Sports Calendar of Events. Like the volume from which it is descended, Chase’s Calendar of Events, now in its 40th year, this book is a compilation of thousands of events from all over North America and the rest of the world. The focus here is sports and recreational activities, and we have been able to cover those topics in greater depth in this volume than in any other in print. Chase’s Sports Calendar of Events is the most thorough and detailed day-by-day record of notable events in the world of sports.
What surprised me a little was that the standard 1997 edition also didn’t include mention of our Blessed Skeptics’ day. Maybe Adrienne hadn’t invented the day until late in 1996, after dates had already been collected for the 1997 Chase’s book. Maybe Adrienne’s dates aren’t featured in the Chase books, despite what Google AI told me. I know it was definitely the case that the speed of information sharing was much slower back then, back when the internet was a lot more rudimentary than it is now.
When I reached the 1998 edition, I was starting to get a little worried. However, between a Recreational Vehicle Show and the South Coast Writer’s Conference and Fireman’s Fish Fry, I found “Skeptics’ Days”, marked as occurring on February the 13th, as well as both March and November the 13th:
SKEPTICS’ DAYS. Feb 13 (also on Mar 13 and Nov 13). National celebration of skepticism. During this day examine those issues which you are most skeptical about. A day to collectively put these issues under a microscope and cut away those attachments that stand in your way of gaining greater success and freedom. Annually, held on Friday 13th. For info: Adrienne Sioux Koopersmith, 1437 W Rosemont, #1W, Chicago, IL 60660-1319. Phone: (773) 743-5341. Fax: (773) 743-5395.
There was Adrienne’s name, along with confirmation that Skeptics’ Days (not day) occurred whenever there was a Friday the 13th - as 1998 indeed had three Friday the 13ths (you can check Bronwyn’s article on this phenomenon from earlier this year to see details of how often Friday the 13ths happen).
Moving forward through the archive, 1999 had a similar entry, but this time sandwiched between Saint Johns Mint Festival and Lucy Stone’s Birth Anniversary, and obviously with a different date:
SKEPTICS’ DAY. Aug 13. National celebration of skepticism. During this day examine those issues which you are most skeptical about. A day to collectively put these issues under a microscope and cut away those attachments that stand in your way of gaining greater success and freedom. Annually, on Friday the 13th. For info: Adrienne Sioux Koopersmith, 1437 W Rosemont, *1W, Chicago, IL 60660-1319. Phone: (773) 743-5341. Fax: (773) 743-5395. E-mail: kooper@interaccess.com.
The text in the 2000 and 2001 editions was very similar, but with dates of October the 13th and July the 13th respectively.
When I got to 2002, I was surprised by a few changes. Firstly, Skeptics’ Day/Days had been replaced by the more auspicious title of “International Skeptics’ Days”, this time on September and December the 13th. Secondly, there was a weird suffix to Adrienne’s listed event, claiming copyright (from 1996, the year International Skeptics’ Day was supposedly created) and mentioning a $7 charge for requests:
INTERNATIONAL SKEPTICS’ DAYS. Sept 13 (also Dec 13). International celebration of The Fine Art of Skepticism. During these days examine those issues which you are most skeptical about. Two days to collectively put these issues under a microscope and cut away those attachments that stand in your way of gaining greater success, freedom and independence. Annually, on Friday the 13th. [©1996] Because of the escalating costs of Eventological® Literature, a charge of $7 must be assessed for each request. Checks are to be made payable to: Adrienne Sioux Koopersmith, 1437 W Rosemont, #1W, Chicago, IL 60660-1319. Phone: (773) 743-5341. Fax: (773) 743-5395. E-mail: adrienne@21stcentury.net.
In addition to this, though, I found the first instance of a “rival” event on the same day, Friday September the 13th:
CSICOP ANNUAL SUPERSTITION BASH. Sept 13 Amherst, NY. The Committee for Scientific Investigation of Claims of the Paranormal (CSICOP) and Skeptical Inquirer Magazine hold an annual Superstition Bash on the first Friday the 13th of each year. Skeptic and science groups across the world also participate by holding their own events. The celebration works to educate people about the dangers and absurdities of superstitious belief and to champion skepticism and critical inquiry. For info: CSICOP/Skeptical Inquirer, PO Box 703, Amherst, NY 14226. E-mail: skeptinq@aol.com. Web: www.csicop.org/superstition.
Yep, the US based Committee for Skeptical Inquiry (CSI), back then known as CSICOP, had decided to make Friday the 13th their own, holding a “Superstition Bash” on September the 13th.
CSICOP’s 2023 event, also listed in Chase’s Calendar of Events, confirms that, like Adrienne’s event, the CSICOP event was designed to move each year to follow Friday the 13ths, this time occurring on June the 13th:
CSICOP ANNUAL SUPERSTITION BASH. June 13. Amherst, NY. The Committee for Scientific Investigation of Claims of the Paranormal (CSICOP) and Skeptical Inquirer Magazine hold an annual Superstition Bash on the first Friday the 13th of each year. Skeptic and science groups across the world also participate by holding their own events. The celebration works to educate people about the dangers and absurdities of superstitious belief and to champion skepticism and critical inquiry. For info: CSICOP/Skeptical Inquirer, PO Box 703, Amherst, NY 14226. E-mail: skeptinq@aol.com. Web: www.csicop.org/superstition.
Following this, the 2004 and 2005 editions of the book were missing, and by 2006 the CSICOP event had disappeared, leaving just Adrienne’s event - which in 2006 were the two Friday the 13ths, in January and October.
INTERNATIONAL SKEPTICS’ DAYS. Jan 13 (also Oct 13). International celebration of the fine art of skepticism. Today, examine those issues which you are most skeptical about. A day to collectively put these issues under a microscope and cut away those attachments that stand in your way of gaining greater success, freedom and independence. Annually, on Friday the 13th. [©1996.] Because of the escalating costs of Eventological® Literature, a charge of $10 must be assessed for each request. Checks are to be made payable to: Adrienne Sioux Koopersmith, 1437 W Rosemont, #1W, Chicago, IL 60660-1319. E-mail: askoopersmith@hotmail.com.
From 2007 onwards, there’s no further mention of any International Skeptics’ Days in the Chase books, leaving the 2006 edition as the last one I can find that lists the event’s dates. I have a strong suspicion that this is why October the 13th, and January 13th, are now considered to be the “official dates” for the event. Nobody ever consciously chose those dates, it’s just that these were the dates Friday the 13th fell on in the last year that Chase’s Calendar of Events mentioned International Skeptics’ Day.
As such, I would like to make my case to David Almandsmith, and to the global Skeptical community, that we return to declaring all Friday the 13ths as International Skeptics’ Day. If David then decides that he wants to celebrate Global Skeptics in the Pub on this auspicious date, he could host it from the evening of Skeptics’ Day on Friday in the US, through to the evening of the next day, Saturday - making the event fall on a weekend globally, and be more accessible for people all around the world. This would also mean that the event would happen in different months on different years, would happen at least once a year, and could be hosted more than once a year if people were keen - up to three times on some years.