[QUOTE=Cow_tipping;286528]Omg, I did just that! Silly date naming convention of those US people.
Change to metric system stop with the comma's in spreadsheets, write the date DDMMYYY and no more yards.
It's 226 unique days in europe, US has 232. :P

* end rant :drama:[/QUOTE]

Would you care to share the European solution with us? Forgive my US-centric construction of the problem. I am surprised that the answers are different for the different date formats!

[QUOTE=NBtarheel_33;286565]I am surprised that the answers are different for the different date formats![/QUOTE]

They are not. :judge:

[QUOTE=ckdo;286569]They are not. :judge:[/QUOTE]

I didn't think so. The dates that get eliminated are those having a "numerator" and "denominator" that have a nontrivial common factor. Obviously, if the "numerator" and "denominator" change roles (as they do in going from an American date to a European one), they still have a nontrivial common factor, and hence the date is still eliminated.

Once we admit the "weird dates", the calendar becomes very sparse! There are only 54 distinct dates out of 366, i.e. nearly six of every seven days get eliminated. I've attached a calendar showing what remains; chances are your birthday doesn't make an appearance...

[QUOTE=NBtarheel_33;288172]Once we admit the "weird dates", the calendar becomes very sparse! There are only 54 distinct dates out of 366, i.e. nearly six of every seven days get eliminated. I've attached a calendar showing what remains; chances are your birthday doesn't make an appearance...[/QUOTE]

really mine does.

[QUOTE=NBtarheel_33;288172]Once we admit the "weird dates", the calendar becomes very sparse! There are only 54 distinct dates out of 366, i.e. nearly six of every seven days get eliminated. I've attached a calendar showing what remains; chances are your birthday doesn't make an appearance...[/QUOTE]

You'll have to explain your logic. I can't for the life of me figure out how _adding_ new dates _reduces_ the available dates.:confused:

[QUOTE=axn;288174]You'll have to explain your logic. I can't for the life of me figure out how _adding_ new dates _reduces_ the available dates.:confused:[/QUOTE]

Remember that the weird dates will ultimately boil down into regular dates (i.e. of the proper form 1/1-1/31, 2/1-2/29, etc.). It seems as though there are many of these weird dates that become regular dates that aren't necessarily eliminated on the first run through.

For example: February 8th (2/8) under the "normal" rules will eliminate the "equivalent" dates 4/16 and 6/24. But if we allow "weird" dates, we also get to throw out 8/32 = 9/1, and 10/40 = 11/9, as well as 12/48 = 1/17. So we get to throw out five dates, instead of just two. It turns out that this kind of thing happens a lot...so much so that only 54 dates are left behind.

Another way to look at it: say we are looking at the dates of the form 1/n (all the January dates). These dates are equivalent to 2/2n, 3/3n, 4/4n, and so on up to 12/12n. That is, we can cancel every even day in February, every third day in March, every fourth day in April, and so on, up to every twelfth day in December. Under the "normal" rules, we have to stop at the end of each month, i.e. we can only cancel, say, April 4, 8, 12, 16, 20, 24, and 28. But under the "weird" rules, we can keep going, cancelling every fourth day in the calendar from April 4th through April 124th, which of course, is August 2nd. There are many more chances to cancel dates out of the calendar.

Clear as mud? :smile: Things do get unwieldy when we start calculating and manipulating weird stuff like 4/124 and 12/372...

[QUOTE=NBtarheel_33;288197]For example: February 8th (2/8) under the "normal" rules will eliminate the "equivalent" dates 4/16 and 6/24. But if we allow "weird" dates, we also get to throw out 8/32 = 9/1, and 10/40 = 11/9, as well as 12/48 = 1/17. So we get to throw out five dates, instead of just two. It turns out that this kind of thing happens a lot...so much so that only 54 dates are left behind.

[/QUOTE]


it's actually more than 5:

1/4=2/8=3/12=4/16=5/20=6/24=7/28=8/32( or 9/1)=9/36(or 10/6) = 10/40 ( or 11/9) = 11/44(or 12/14) = 12/48 ( or 1/17) starting with this new first month date it continues to cycle unless I missed a rule.