5 Weekends in 1 Month Happens More Often Than Every 823 Years
5 Fridays, 5 Saturdays, and 5 Sundays in a month? It happens only once every 823 years! This popular urban myth has been circulating the internet for a while. However, it is precisely that: a myth.
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:
May 2020 will have 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 right. May 2020 does have 5 Fridays, 5 Saturdays, and 5 Sundays, and so does May 2848. But this is neither special nor unusual. You won't need to wait for another 823 years to see this weekday combination to occur in the month of May. Just 6 more years, because in 2026, May also has 5 Fridays, 5 Saturdays, and 5 Sundays.
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.
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, March 2020 has 5 Sundays, 5 Mondays, and 5 Tuesdays. July 2020 has 5 Wednesdays, 5 Thursdays, and 5 Fridays.
There are 7 different days a month can start on. 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 in a leap year, January and July look the same.
5-Day Combinations in a Month
|Dates:||1/ 8 / 15 / 22 / 29||2 / 9 / 16 / 23 / 30||3 / 10 / 17 / 24 / 31||Comments|
|January 2020||5 Wednesdays||5 Thursdays||5 Fridays||Same as July 2020|
|March 2020||5 Sundays||5 Mondays||5 Tuesdays|
|May 2020||5 Fridays||5 Saturdays||5 Sundays|
|July 2020||5 Wednesdays||5 Thursdays||5 Fridays||Same as January 2020|
|August 2020||5 Saturdays||5 Sundays||5 Mondays|
|October 2020||5 Thursdays||5 Fridays||5 Saturdays|
|December 2020||5 Tuesdays||5 Wednesdays||5 Thursdays|
|January 2021||5 Friday||5 Saturday||5 Sunday||Same as October 2021|
|March 2021||5 Mondays||5 Tuesdays||5 Wednesdays|
|May 2021||5 Saturdays||5 Sundays||5 Mondays|
|July 2021||5 Thursdays||5 Fridays||5 Saturdays|
|August 2021||5 Sundays||5 Mondays||5 Tuesdays|
|October 2021||5 Fridays||5 Saturdays||5 Sundays||Same as January 2021|
|December 2021||5 Wednesdays||5 Thursdays||5 Fridays|