*some large number*> of years (every time I see it, the number is different).

Except, you know, January of this year. Or May last year. So, fail.

Maybe they all meant that there hasn't been any

*Octobers*with 5 Fridays, Saturdays and Sundays (FSSs) in that many years. My answer: go go gadget Ruby! Here's a little script that will find the last October which had 5 FSSs:

i = 2009 # a month with 31 days will have 5 FSSs iff the first # day of the month is a Friday begin day = Date.parse("#{i}-10-01") i -= 1 end until day.wday == 5 puts day.yearTurns out the answer is....2004! Sure enough looking at the calendar for October 2004 it does indeed have 5 FSSs. Before that? 1999. Before that? 1993. I could go on but I'm getting bored of this.

## 4 comments:

It seems that your post inspired this: http://rosettacode.org/wiki/Five_weekends

Thanks!

Oh damn! I love Rosetta Code, I suppose I should have thought of putting that up as a problem... oh well. I put up a Ruby version :)

Well, yeah. This blog's in my blogroll, and it isn't the first time I've stolen a task idea from you. I mentioned the post in the IRC channel, and Mwn3d put it together. :)

I'm surprised anyone would fall for that. Which day of the week a date falls on follows an easy to work out path. The day of the week a date will fall on advances one day a year for each year, except leap years when it advances two days*. Given this, it's easy to see that we'd expect the pattern you note, with 5 or 6 years between occurrences(Depending exactly how the leap years fall in the cycle). A rarer thing would actually be when there is a longer than 6 year gap between 5 weekend October years(which day is skipped on leap year follows a 5-day pattern, so it will hit all the days eventually, so you just need to wait 8*4 years for it to skip the same day). As far as I can tell, that should only happen ever 32 years or so.

*how do we know this:

365%7= 1

366%7= 2

or you might have just noticed it like I did when I was like 10.

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