# Calendar faux meme – “every 823 years”

The year 2100 is NOT a leap year.

Several people I know IRL, intelligent people, have said they got a text or saw a Facebook message. It reads, e.g. “The month of December 2018 will have 5 Saturdays, 5 Sundays, and 5 Mondays. It only happens once every 823 years.”

When I first saw this meme a half decade or more ago, I knew instantly that it had to be untrue. The reason was that, as a kid, I devoured the World Almanac every year.

About a third of the way through was the calendar section, and it indicated that there were only 14 ways a calendar year could be constructed. January 1 starts on one of the seven days; it’s a leap year or it’s not. Seven times two is fourteen.

In a non-leap year, if January 1 is on a Sunday, we had experienced that same pattern in 2006, 2017 and will again in 2023. Calendars repeat. 2018 looks just like 2007; 2029 and 2035 will be carbon copies.

(I’m talking calendar days, not moving holidays such as Easter or Yom Kippur.)

In general, a calendar will repeat every six or eleven years, depending on whether it hits one or two leap years in between. So 2002 is the model for 2013, 2019, 2030, 2041, 2047, et al.

Even leap years repeat, obviously less frequently. The calendars for 1992, 2020 and 2048 are the same.

One way to prove that the specific meme is a myth is to go to Time and Date for “When is Saturday the 1st?” Eliminating the months with less than 31 days:
May 2010; January 2011; October 2011; December 2012; March 2014; August 2015; October 2016; July 2017; December 2018; August 2020.

Basically I look at the perpetual calendar for 1801 to 2100 and see the repeating patterns.

Note, BTW, the year 2100 is NOT a leap year. “Any year evenly divisible by four is a leap year, except centesimal years (years ending in two zeros) which are considered common years and thus have the typical 365 days, unless they are evenly divisible by 400. Therefore, 1600 and 2000 are leap years, while 1700, 1800, 1900 and 2100 are not.”

## Author: Roger

I'm a librarian. i hear music, even when it's not being played. I used to work at a comic book store, and it still informs my life. I won once on JEOPARDY! - ditto.

## 9 thoughts on “Calendar faux meme – “every 823 years””

1. As you proove by this blogpost… this is just one of the countless things that are said by many people who follow other people without using the gift they got, intelligence, and keep alive the wrong things

2. That’s a lot of investigation and math. – Margy

3. Roger,

Unfortunately, there are far too many hoaxes floating around on FB and some are quite believable. They still get me on occasion but I learned years ago to check out things that I want to share to make sure it’s legit because someone in my friend circle is usually smarter than me and will catch my screw up every time, then I feel like a real idiot. lol

Thank you for cultivating my brain for better clarification on how the calendar years work.

4. I can happily ignore that meme now, thank you very much. ðŸ™‚

5. Roger ~ great research for C ~ very informative ~ thanks ^_^

Happy Day to you,
A ShutterBug Explores,
aka (A Creative Harbor)

6. this is great, Roger! I really dislike those memes, and the way people share and repost misinformation. I love that you took the time to deconstruct this, and share the truth of your findings. we could make your blog ‘go viral’ by posting it as a comment beneath each such meme! ðŸ˜€

7. Bev Baird says:

Great post Roger.You sure cleared that myth up! I have a small perpetual calendar that I switch every month.

8. Oh.. thank you Roger, this needed to be said and you said it!!

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