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Why 5 Fridays, 5 Saturdays and 5 Sundays don’t occur every 823 years

The Truth is…

The first three 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 has 5 Fridays, 5 Saturdays, and 5 Sundays. And this happens much more often than every 823 years.

Have a look at our calendars and take it to the test!

Illustration image

Proof in cold print: August 2014 and August 2837
are not even the same.

Repeating Calendars

August 2014 has 5 Fridays, 5 Saturdays, and 5 Sundays. The next time that the 2014 calendar repeats itself is in the year 2025, which is only 11 years later. What’s more, a calendar month that contains 5 Fridays, 5 Saturdays and 5 Sundays occurs nearly every year: After August 2014, the next occurrence is in May 2015.

It does not repeat after 823 years at all

Not only does a month with 5 Fridays, 5 Saturdays, and 5 Sundays occur much more frequently than the urban myth wants us to believe; the calendar for any year does not even match with the calendar for the year 823 years into the future (see picture comparing August 2014 with August 2837).

For instance, August 2014 has 5 Fridays, Saturdays and Sundays. 823 years later, August 2837 has 5 Saturdays, Sundays and Mondays. That is a 5th Monday instead of a 5th Friday.

Variations of the urban myth:

How recurring calendar months work

Every year has 7 months with 31 days. Each of these 7 months has three weekdays of which there are 5. There are 7 different days a month can start on. So on average, over time, each combination happens once yearly. But for each individual year, there are only 6 of 7 combinations, and two 31-day months start on the same weekday.
In a common/regular year, January and October look the same. In a leap year, January and July look the same.

5 of the same day in one month in 2014

Days that occur 5 times, on these dates:
1 / 8 / 15 / 222 / 9 / 16 / 233 / 10 / 17 / 24
31 day month29th of month30th of month31st of monthComments
January 20145 Wednesdays5 Thursdays5 FridaysSame as October
March 20145 Saturdays5 Sundays5 Mondays
May 20145 Thursdays5 Fridays5 Saturdays
July 20145 Tuesdays5 Wednesdays5 Thursdays
August 20145 Fridays5 Saturdays5 Sundays
October 20145 Wednesdays5 Thursdays5 FridaysSame as January
December 20145 Mondays5 Tuesdays5 Wednesdays
Not occurring in 2014: A month with 5 Sundays, 5 Mondays, 5 Tuesdays

5 of the same day in one month in 2015

Days that occur 5 times, on these dates:
1 / 8 / 15 / 222 / 9 / 16 / 233 / 10 / 17 / 24
31 day month29th of month30th of month31st of monthComments
January 20155 Thursdays5 Fridays5 SaturdaysSame as October
March 20155 Sundays5 Mondays5 Tuesdays
May 20155 Fridays5 Saturdays5 Sundays
July 20155 Wednesdays5 Thursdays5 Fridays
August 20155 Saturdays5 Sundays5 Mondays
October 20155 Thursdays5 Fridays5 SaturdaysSame as January
December 20155 Tuesdays5 Wednesdays5 Thursdays
Not occurring in 2015: A month with 5 Mondays, 5 Tuesdays, 5 Wednesdays

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