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Admin (Admin)
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Post Number: 1114
Registered: 7-2006
Posted on Tuesday, October 08, 2013 - 4:17 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

It happened this year. The last time it happened was in 1987. What is it?
Doriana (Doriana)
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Post Number: 43
Registered: 9-2013
Posted on Tuesday, October 08, 2013 - 4:40 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Ooooh I think I know this one! Possible $poyler e-mailed.
Balin (Balin)
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Post Number: 47
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Posted on Tuesday, October 08, 2013 - 5:08 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Are the digits of the year relevant?
Admin (Admin)
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Username: Admin

Post Number: 1115
Registered: 7-2006
Posted on Tuesday, October 08, 2013 - 5:13 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Balin,

You guys are too good:

Are the digits of the year relevant?

YES
Wizardofnz (Wizardofnz)
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Post Number: 633
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Posted on Tuesday, October 08, 2013 - 11:04 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I understand that this has never happened in any year in which a film was copyrighted.
King_louie2 (King_louie2)
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Post Number: 42
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Posted on Tuesday, October 08, 2013 - 11:51 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Year given in Roman numerals relevant?
Admin (Admin)
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Username: Admin

Post Number: 1116
Registered: 7-2006
Posted on Wednesday, October 09, 2013 - 10:02 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Louie,

Year given in Roman numerals relevant?

NO
Gregoryuconn (Gregoryuconn)
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Username: Gregoryuconn

Post Number: 5
Registered: 10-2013
Posted on Wednesday, October 09, 2013 - 3:50 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Three consecutive digits in a year?
Peter365 (Peter365)
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Username: Peter365

Post Number: 4914
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Posted on Wednesday, October 09, 2013 - 3:55 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Oh I've just worked this out . That's very clever.
Psydkik (Psydkik)
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Post Number: 178
Registered: 9-2013
Posted on Wednesday, October 09, 2013 - 3:56 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

A moment when the year 2000 was thirteen years away? :-S
Psydkik (Psydkik)
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Post Number: 181
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Posted on Wednesday, October 09, 2013 - 6:30 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Ah... I think I might have got it now - does it depend on my date format whether this happened in 2013, or whether this didn't happen in 2013, and won't happen until the year 2345? (But either way, it did happen in 1987?)
Admin (Admin)
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Post Number: 1117
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Posted on Thursday, October 10, 2013 - 8:49 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Psy

Ah... I think I might have got it now - does it depend on my date format whether this happened in 2013, or whether this didn't happen in 2013, and won't happen until the year 2345? (But either way, it did happen in 1987?)

NO. IT WILL HAPPEN AGAIN IN 2014.
Psydkik (Psydkik)
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Post Number: 188
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Posted on Thursday, October 10, 2013 - 9:34 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Gah, ok, I don't know again then!

Did it happen just once in 2013? Or multiple times?
What about in 1987 - once or more?
And in 2014 - once or more?

Did it happen on a specific day and month on each occasion? Or was it a year-long or month-long event?
Psydkik (Psydkik)
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Post Number: 197
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Posted on Thursday, October 10, 2013 - 9:46 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

And just to check I wasn't being over-cryptic earlier... it's not the thing I was thinking of before, that happened 30 times in 2013, but 39 times in 1987?
Biograd (Biograd)
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Username: Biograd

Post Number: 10
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Posted on Thursday, October 10, 2013 - 9:50 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Is it simply the fact that all of the digits in the year are different? In 1988 and 1989 the last digit is a repeat of an earlier digit. In all of the years 199x and 200x, the middle two digits are the same. And finally in 2010, 2011, and 2012 the last digit is again a repeat.

But the digits will all be unique from now until 2019, after which there will be another ten-year period of repeated 2's.
Yojimbo (Yojimbo)
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Post Number: 127
Registered: 9-2013
Posted on Friday, October 11, 2013 - 1:58 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Beaten to it -- while working in the forest today, I became aware of Biograd's posted phenomenon.
Wizardofnz (Wizardofnz)
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Post Number: 657
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Posted on Friday, October 11, 2013 - 2:32 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I think I've figured out Psydkik's proposed solution, too. Definitely more complex. Perhaps you could host that as a puzzle afterwards :P
Admin (Admin)
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Username: Admin

Post Number: 1118
Registered: 7-2006
Posted on Friday, October 11, 2013 - 9:48 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

* * * SPOILER * * *

YO BIOGRAD

Is it simply the fact that all of the digits in the year are different? In 1988 and 1989 the last digit is a repeat of an earlier digit. In all of the years 199x and 200x, the middle two digits are the same. And finally in 2010, 2011, and 2012 the last digit is again a repeat.

CORRECT

NOW CAN PSY SHARE HIS SOLUTION PLEASE?
Psydkik (Psydkik)
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Username: Psydkik

Post Number: 201
Registered: 9-2013
Posted on Friday, October 11, 2013 - 2:45 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I can let you work out my alternative solutions as a continuation of the puzzle, if you don't mind me hijacking the thread from here on? - it's not really lateral thinking any more, but it's still a puzzle.

I can give you three different 'date formats':

DATE FORMAT A:
The answer is that 1987 and 2013 both have different digits, as does 2014. Puzzle solved :-)

DATE FORMAT B:
1987 has 39
2013 has 30
2014 has 30
2345 has 40

DATE FORMAT C:
1987 has 12
2013 has 0
2014 has 0
2345 has 12


1a) What are the "Date Formats"
1b) specifically what date formats do you need for the answers "A", "B" and "C" above
1c) what do the other numbers (39, 30, 12, etc) represent?

And for bonus points for the mathematically/computationally confident:
2) with date formats "B" and "C", how many are there for the year 3025? and for 2597?
3) Which year between 1900 and 9999 has the most in each of "B" and "C" formats? And can you say roughly in English why?

And I'm fairly confident all my maths is right but apologies if I've made any mistakes! :-)

If no-one looks particularly interested in pursuing this more-mathematical-than-usual puzzle for LTPF, I'll just post a straightforward spolier in a few days.
Balin (Balin)
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Username: Balin

Post Number: 80
Registered: 9-2013
Posted on Friday, October 11, 2013 - 10:29 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I wish I could say I'd figured this out earlier, but I got stuck after my first question.
Docd (Docd)
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Username: Docd

Post Number: 196
Registered: 12-2004
Posted on Tuesday, October 15, 2013 - 3:40 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Format "B"- 3025 has 50, 2597 has 45
Format "C"- 3025 has 0, 2597 has 13
Correct, Psydkik?
Psydkik (Psydkik)
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Post Number: 251
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Posted on Tuesday, October 15, 2013 - 5:43 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Docd:

Format "B"- 3025 has 50, 2597 has 45
Format "C"- 3025 has 0, 2597 has 13
Correct, Psydkik?

Spot on :-)

Got to rush off now but will post a spoiler later in the week...
Docd (Docd)
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Username: Docd

Post Number: 197
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Posted on Wednesday, October 16, 2013 - 8:31 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

OK. It looks like date Format "B" is D:M:YYYY (or M:D:YYYY) where D is the date (1 or 2 digits), M is the month (1 or 2 digits) and YYYY is the year (all 4 digits). Format "C" is DD:MM:YYYY, using a 0 for DD and MM if needed to make them 2 digits.

The other number represents the number of times in year YYYY that all digits are different, in that format.

By my back-of-an-envelope calculations the highest score in Format B is 77. This will occur in the 18 years consisting of the digits 4,6,9,0 (with 0 not the initial digit).
Format C is trickier. I think the maximum score is 26. This occurs in years when 3 of the 4 digits are 4,6,9 and the 4th digit is one of 5,7, or 8. 72 years in total.
Psydkik (Psydkik)
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Username: Psydkik

Post Number: 262
Registered: 9-2013
Posted on Wednesday, October 16, 2013 - 12:33 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

***************Post-spoiler Spoiler***************

Docd is indeed right, and other than I think his "26" should be "33", it's as he says.



So the original puzzle was just looking at the year.

A: Date Format: yyyy

1987 contains 4 different digits.
2013 contains 4 different digits.
But no year in between does.


But I was considering specific dates rather than just the year.

B: Date Format: d/m/yyyy

For example, the first of January 2013 is 1/1/2013, which has duplicate 1's.

But there are a few days in 2013 it works for. The first one of the year is 5 April 2013, which is 5/4/2013, six digits all different. There are in total thirty dates in 2013 which work: the 4th to the 9th of each of April, May, June, July, August and September (except for the day that matches the month).

The last day in 1987 that works is 30 Jun 1987: 30/6/1987 Just before that, 25/06/1987 also works.


But when I write 1 January 2013 in numbers, I don't usually put 1/1/2013, I usually put 01/01/2013, so that it's always a predicable length.

C: Date Format: dd/mm/yyyy

In 1987, 25 June worked earlier: 25/6/1987. It also works in this new format: 25/06/1987, and as it turns out, that was the last time it would work for over three hundred and fifty years! Because 30/06/1987 now doesn't work on account of having two 0's.

And earlier, 5/4/2013 was a valid option. But in dd/mm/yyyy format, it becomes 05/04/2013, which now has three 0's, and isn't allowed.

As it turns out, nothing works now in 2013. Because:

- you can't have any year with both a 0 and a 1 in it, because all months have either a 0 or 1 in them.
- you can't have any year with both a 0 and a 2 in it, because the only month which doesn't have a 0 or 2 in it is Nov, which is 11, with a double-1.
- you can't have any year with both a 1 and a 2 in it, because the month would then have to be one of 03-09 - which uses the 0 - and then there are no days left because all days from 01-31 use either a 0, 1 or 2 which you've already used.

So there aren't any dates for quite a while which work in dd/mm/yyyy format. You have to wait until the year 2345 before you get a year without two of 0/1/2 in it, so the seventeenth of June 2345 - 17/06/2345 - will be a significant day! Remember to celebrate it!

----------------------------

And if you care enough to investigate further, you'll find for example, as Docd did:

In 3025, there are 50 dates that work in d/m/yyyy format, but 0 that work in dd/mm/yyyy format.
In 2597, there are 45 dates that work in d/m/yyyy format, but 13 that work in dd/mm/yyyy format.

The year with the most different-digit-dates will be different in the two different formats.

In d/m/yyyy format, you get the highest number when you use the 9 (because Feb has only 28 days), 0 (also due to Feb but mainly because Oct already clashes a lot due to having a 1 in it as well, so less to lose by using the 0), and the 4 and 6 because there are fewer days in April and June than the others, so fewer clashes. You still can't use 1, 2 or 3 because they clash with lots of days, so putting together 4, 6, 9 and 0, you can get the most valid dates in the year 4690, 4096, 6094, 9046 etc. A total of 77 in each.

In dd/mm/yyyy format, it's similar, except you now can't use the 0. Instead you have to use either the 5, 7 or 8 in addition to the 4, 6 and 9. So 4569, 4769, 4869, 9684, 6945, 4967, etc. A total of 33 in each.


And no, I didn't work that all out in my head or even on backs of envelopes; I got Excel to do most of the work for me ;-) The 'Solver' Add-in is a great little tool!
Gregoryuconn (Gregoryuconn)
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Username: Gregoryuconn

Post Number: 46
Registered: 10-2013
Posted on Thursday, October 17, 2013 - 1:57 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Wait? My professor didn't invent solver? It's available everywhere? Because he claims to have done so when we used it in class.
Psydkik (Psydkik)
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Username: Psydkik

Post Number: 276
Registered: 9-2013
Posted on Thursday, October 17, 2013 - 4:44 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

"Solver" in Excel is a standard Add-in ... ie it's part of everyone's excel, it's just that you can't see it until you actively 'add-' it '-in'.

To do this on your own version of MS Excel, just:

1) On the menu, go to File -> Options
2) Go to "Add-ins" tab
3) At the bottom in the drop-down menu, select "Manage: 'Excel Add-ins'", and click "Go..."
4) Click the box for "Solver Add-in", and click "OK"
5) Go to your "Data" menu and you'll find it now appears on there.

It's possible your professor invented it... if he used to work for Microsoft or sold it to them - or perhaps helped invent a previous computerised version of the same method - all based on a Linear Programming method which wikipedia says dates back to 1939 ;-)
Psydkik (Psydkik)
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Username: Psydkik

Post Number: 277
Registered: 9-2013
Posted on Thursday, October 17, 2013 - 4:45 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

(that's on my newish version of excel - might differ slightly for different versions, but search for "Add-ins" and you'll find it)

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