5 Weekends in 1 Month Happens More Often Than Every 823 Years

Before you get too excited about this once-in-a-lifetime event and start telling your family and friends, know this: any such claims are false. Combinations of days like 5 Fridays, 5 Saturdays, and 5 Sundays occur much more often than every 823 years!

The 823 Years Myth

If you have an email or a social media account, chances are that you have come across a viral post that claims an upcoming month has a rare combination of weekdays. Share it, the message states, or beware of some bad luck.

A recent version goes something like this:

December 2023 has 5 Fridays, 5 Saturdays, and 5 Sundays. This happens only once every 823 years. The Chinese call it “silver pockets full” or “money bags.”

The email is partially correct. December 2023 does have 5 Fridays, 5 Saturdays, and 5 Sundays. But this is neither special nor unusual. You won’t need to wait for another 823 years for this weekday combination to occur. (In fact, it doesn’t even happen in the year 2846, which is 823 years after the year 2023!)

A calendar month that contains 5 Fridays, 5 Saturdays, and 5 Sundays actually occurs nearly every year—March 2024, August 2025, and May 2026 all have the same weekday pattern.

First Day of the Month

The weekday combinations these 823-year messages refer to aren’t exceptional either. A quick look at a calendar will show that the first 3 weekdays of any 31-day month will be repeated 5 times in that month. So, any month that has 31 days and begins on a Friday will have 5 Fridays, 5 Saturdays, and 5 Sundays. Similarly, any 31-day month that begins on a Tuesday will have 5 Tuesdays, 5 Wednesdays, and 5 Thursdays.

Put it to the test in our calendar

Recurring Monthly Calendars

Ready for some math? Here’s a more mathematical reasoning of why the 823-year claim is a myth:

Every year has 7 months with 31 days. Each of these months has at least 3 weekdays that happen 5 times during the month. For example, August 2023 has 5 Tuesdays, 5 Wednesdays, and 5 Thursdays. October 2023 has 5 Sundays, 5 Mondays, and 5 Tuesdays.

There are 7 different days a month can start. So, on average, the combination of any 3 days occurring 5 times in a calendar month will happen once a year.

In any given year, there are only 6 such combinations of days. This is because 2 months with 31 days start on the same weekday. In a common year, January and October have the same calendar, while January and July look the same in a leap year.

The Doomsday Rule for calendars

* 2023 is a common year, 2024 is a leap year.

Topics: Calendar, Fun