## Friday, October 15, 2010

### A Special October?

This October is very special. It has 5 Fridays, 5 Saturdays and 5
Sundays all in 1 month. This happens once in 823 years. These are known
as money bags. Pass this along to 8 good people and money will appear in
4 days based on the Chinese Feng Shui. Those who stop it will experience
none.

Well,I received this message over 4 days ago and no money appeared so far. I am sending it now to over 1,000 good people and will let you what comes. While we may not be able to predict the fortune, I think we can check whether this October is indeed as special as stated: Is it true that October that has 5 Fridays, 5 Saturdays and 5 Sundays happens only once in 823 years? Seems suspiciously rare

Kim said...

Any October that starts on a Friday will have 5 Fridays, 5 Saturdays and 5 Sundays. That should happen one October in 7.

Kim said...

Actually, the presence of Leap Year messes this up a bit, so it's not precisely every 7 years. In the first century of 2000 we have 2004, 2010, 2021, 2027, 2032, 2038, 2049, 2055, 2060, 2066, 2077, 2083, 2088, and 2094.

Maria said...

Can someone invite Kim for a meeting every Friday morning? She is solving all the puzzles and she is so good at them!

Kim, it looks like there is a pattern in your year list. Difference between the years is: 6,11,6,5,6,11,6,5,...
Why is this happening? Can you explain mathematically?

Wang said...

Actually, this last January had 5 Fridays, 5 Saturdays and 5 Sundays. That alone should say that it doesn't just happen once in every 823 years - unless the wording is saying this happens in Oct but then again, Kim just proved that it happens more often than that =)

Tom said...

Got here late today, sorry. Yes, not that rare at all to have such a month if there are 31 days, as in Octobers. Happens again July 2011. A myth. Tom

Donna said...

The next time we have an October with 5 Fridays, Saturdays and Sundays will be in 2021. I went about it from a slightly different approach, assuming every time Oct. 31 occurs on a Sunday, there will be 5 complete weekends. I took into account the leap years in 2016 and 2020. So it happens approximately every 11 years or so....depending where leap years fall. :)

Donna said...

Sorry....actually just read Kim's and Maria's comments above. Don't know if I can explain mathematically the pattern mentioned above easily, but the 5 year intervals occur when a leap year immediately follows the year with the 5 weekends. The 6 year intervals occur when a leap year coincides with the year with the 5 weekends, and the 11 year intervals occur when a leap year occurs 2 years after the year with the 5 weekends.

Kim said...

The increment depends on the number of leap years between the 5-weekend Octobers. If there were no leap years, we'd move back one day each year, such that this would happen every 7 years. When there's one leap year in between, it happens every 6 years. But sometimes there are two Leap Years in between, and then we either get a 5 year interval, OR we find we skip over special 5-weekend October and then we end up with THREE Leap Years in between. So, we get either 6, 5 or 11 depending on the intervening Leap Years.

Maria said...

Very very interesting. A well-deserved point for Kim and bravissimo to everyone else who participated.
The money-bag prophecy verification is saying: "beep, beep. lie is detected."

Look for a new Halloween puzzle in the Friday newsletter.