5 Weekends in 1 Month Happens More Often Than Every 823 Years
5 Fridays, 5 Saturdays, and 5 Sundays in a month – happens only every 823 years? This popular urban myth has been circulating on 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. Special 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 own an email, Twitter, Facebook or any other social media account, chances are that you have come across an email or a post that claims an upcoming month has a very rare specific combination of days. A recent version goes something like this:
December 2017 will have 5 Fridays, 5 Saturdays, and 5 Sundays. This happens only once every 823 years. The Chinese call it "silver pockets full".
The email is right in that December 2017 will have 5 Fridays, 5 Saturdays, and 5 Sundays. But this is nothing special or unusual. You will not have to wait another 823 years for the next time this happens in the month of December. Only 4 years later, in 2021, December will also have 5 Fridays, 5 Saturdays, and 5 Sundays.
Nearly Every Year
In fact, a calendar month that contains 5 Fridays, 5 Saturdays, and 5 Sundays occurs nearly every year. In 2019 March will have 5 Fridays, 5 Saturdays, and 5 Sundays.
In fact, the calendar 823 years in the future is not even the same as the calendar of the month in the many versions of the hoax! For instance, August 2014 had 5 Fridays, 5 Saturdays, and 5 Sundays. 823 years later, August 2837 has 5 Saturdays, 5 Sundays, and 5 Mondays.
Not So Special
The combinations of days these messages or emails refer to are also not very special. This is because the first 3 weekdays of any 31-day month are repeated 5 times within 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
Here's a more mathematical reasoning why the 823 year claim is a myth:
Every year has 7 months with 31 days. Each of these months have at least 3 weekdays that happen 5 times during the month. For example, August 2014 had 5 Fridays, 5 Saturdays, and 5 Sundays. October 2014 had 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 occuring 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 Combos in the Same Month
|Days that occur 5 times, on these dates:|
|1 / 8 / 15 / 22||2 / 9 / 16 / 23||3 / 10 / 17 / 24|
|31-day month||29th of month||30th of month||31st of month||Comments|
|January 2016||5 Fridays||5 Saturdays||5 Sundays||Same as July|
|March 2016||5 Tuesdays||5 Wednesdays||5 Thursdays|
|May 2016||5 Sundays||5 Mondays||5 Tuesdays|
|July 2016||5 Fridays||5 Saturdays||5 Sundays||Same as January|
|August 2016||5 Mondays||5 Tuesdays||5 Wednesdays|
|October 2016||5 Saturdays||5 Sundays||5 Mondays|
|December 2016||5 Thursdays||5 Fridays||5 Saturdays|
Not in 2016: A month with 5 Wednesdays, 5 Thursdays, 5 Fridays
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Special Date Combinations
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