News for hackers. Stuff that matters.
Re:Show HN: Every Day Is Pi Day by Jaruzel on Tuesday March 14, 2017 @10:33AM (#13867756)
For most of us in the world, No Day is Pi Day.

http://imgur.com/1r5QpQu

Re:Show HN: Every Day Is Pi Day by trcollinson on Tuesday March 14, 2017 @10:35AM (#13867776)
It seems this Show HN proves you rather wrong. I understand the point, you use a different format for your dates than the US. But the point of this Show HN is that all number sequences can be found within the digits of pi quite easily.

Very neat demonstration!

Re:Show HN: Every Day Is Pi Day by oneeyedpigeon on Tuesday March 14, 2017 @12:07PM (#13868716)
> all number sequences can be found within the digits of pi quite easily

I dispute that, although I guess the general brute-force solution is 'easy' given infinite time.

Re:Show HN: Every Day Is Pi Day by geofft on Tuesday March 14, 2017 @12:20PM (#13868844)
Yeah, this isn't known to be true. pi has not been proven to be a disjunctive number (a real number whose expansion contains all possible finite strings), let alone a normal number (where all finite strings occur with the probability you'd expect if the digits were random). Both of these, however, are generally conjectured to be true, but it's just a conjecture.

https://oeis.org/wiki/Disjunctive_numbers#Is_pi_a_disjunctiv...

https://en.wikipedia.org/wiki/Normal_number

Re:Show HN: Every Day Is Pi Day by rnhmjoj on Tuesday March 14, 2017 @01:40PM (#13869674)
Re:Show HN: Every Day Is Pi Day by lutusp on Tuesday March 14, 2017 @01:11PM (#13869405)
>> all number sequences can be found within the digits of pi quite easily

> I dispute that, although I guess the general brute-force solution is 'easy' given infinite time.

Look at it this way -- if it were not true, then the digits of Pi would not be normally distributed (see https://en.wikipedia.org/wiki/Normal_number), and that would be a rather extraordinary mathematical finding.

If Pi's digits are normally distributed, then one can reliably predict the time required for finding any particular digit sequence using probability theory. And given the presumption of normalcy, that probability is the same for any digit sequence of a given length.

The probability for finding a given test digit sequence in the first 100 million digits of Pi is given here:

https://www.angio.net/pi/whynotpi.html

But it has to be emphasized that, given a finite test sequence and an infinite sequence of Pi's digits as a search space, the probability is 1.0.

Re:Show HN: Every Day Is Pi Day by oneeyedpigeon on Tuesday March 14, 2017 @01:41PM (#13869685)
You're both giving me too much credit. I was merely making the less sophisticated point that it's not 'easy' to find an arbitrary-length sequence in pi because that might take longer than the lifespan of the universe when the needle gets long enough. Your response was much more interesting, though, thanks :)
[dead]
Re:Show HN: Every Day Is Pi Day by atonse on Tuesday March 14, 2017 @12:39PM (#13869039)
It's always fashionable to make fun of the US doing things its own way, when that's just seldom true.

You're mostly right that nobody else uses MMDDYYYY (although many countries use it as a secondary format). But it's not like there's a consistent format that _everyone else_ uses.

There are 2-3 different formats spread around the world, with no real consistency in why some pick a particular format.

Re:Show HN: Every Day Is Pi Day by tossaway1 on Tuesday March 14, 2017 @11:58AM (#13868616)
> 'I' use? I think you'll find everyone uses a different format than the US.

The plural of "you" in English is"you"...

Re:Show HN: Every Day Is Pi Day by ska on Tuesday March 14, 2017 @01:13PM (#13869419)

   Everyone already knows this.
That's funny, because we have not proven it to be true.
Re:Show HN: Every Day Is Pi Day by lutusp on Tuesday March 14, 2017 @02:24PM (#13870087)
It's also an argumentum ad populum.
Re:Show HN: Every Day Is Pi Day by justusthane on Tuesday March 14, 2017 @11:23AM (#13868218)
everyone uses a different format than the US.

'Everyone uses'? What about all the people in the U.S.?

Re:Show HN: Every Day Is Pi Day by fao_ on Tuesday March 14, 2017 @10:47AM (#13867877)
Actually ISO 8601 states that the datecode format that should be used is

YYYY-MM-DDTHH:MM:SS+<OFFSET>

in this format, Pi day is:

2017-03-14 (The rest of the complete format omitted since it is not strictly relevant)

Re:Show HN: Every Day Is Pi Day by Jaruzel on Tuesday March 14, 2017 @10:51AM (#13867904)
Except that's not what people mean when the say 'Pi Day' - they mean the US date format of 3-14.
Re:Show HN: Every Day Is Pi Day by fao_ on Tuesday March 14, 2017 @11:41AM (#13868400)
If both work, and the one interpretation overlaps and is an international standard, who cares?
Re:Show HN: Every Day Is Pi Day by athenot on Tuesday March 14, 2017 @12:31PM (#13868951)
Maybe that day can be written 2017-π to preserve both the pun and (if not the letter) the spirit of ISO notation. In that sense, it's Pi day for a given year.
Re:Show HN: Every Day Is Pi Day by GlennS on Tuesday March 14, 2017 @10:46AM (#13867859)
Also works with YYYY-MM-DD...

Although admittedly I too find the US date system's wrong-endianness pretty annoying.

Re:Show HN: Every Day Is Pi Day by TallGuyShort on Tuesday March 14, 2017 @11:19AM (#13868172)
I've always been surprised that Pi Day is primarily evangelized by so many math / science / CS folks, when I would think it would be precisely these folks who hate the MM/DD/YYYY format. ISO format soothes my soul like a warm slice of apple pie with ice cream.
Re:Show HN: Every Day Is Pi Day by SAI_Peregrinus on Tuesday March 14, 2017 @01:07PM (#13869349)
Pi Day is the same in Drunk Endian (US) and Big Endian (ISO Standard) formats (March 14th). It's different in Little Endian (Traditional European) format.
Re:Show HN: Every Day Is Pi Day by TallGuyShort on Tuesday March 14, 2017 @10:19PM (#13873275)
Yeah this thought mainly occurred to me when a big hubbub was made about 3.1415 day (3/14/15, or MM/DD/YYYY).
Re:Show HN: Every Day Is Pi Day by clarkcox3 on Tuesday March 14, 2017 @12:37PM (#13869018)
And, in the ISO format, when omitting the year, it's still 3-14.
Re:Show HN: Every Day Is Pi Day by athenot on Tuesday March 14, 2017 @12:36PM (#13869012)
I have been dating all official documents in ISO-8601 format and never had an issue with that in over 15 years. This includes bank forms, checks, contracts, and many other informal docs. Same for when my birthdate is requested of me. Even if the form has specific spaces for MM/DD/YYYY, I just write over it with the pen.
Re:Show HN: Every Day Is Pi Day by Shivatron on Tuesday March 14, 2017 @12:46PM (#13869109)
I assume you have the luxury of an unambiguous birthday (eg. 01-13). I imagine if I wrote 11-12 on a form without regard to what the specific spaces say, it would be regularly misinterpreted in the US.
Re:Show HN: Every Day Is Pi Day by athenot on Tuesday March 14, 2017 @06:00PM (#13871870)
No, both day and month are ≤ 12. Yet it seems to be OK.
Re:Show HN: Every Day Is Pi Day by ska on Tuesday March 14, 2017 @01:14PM (#13869425)
Not if you include the year.
Re:Show HN: Every Day Is Pi Day by teekert on Tuesday March 14, 2017 @12:20PM (#13868838)
I once found myself confused as to how to date a US patent application, I was happy though to find that it was August 8th at the time.
Re:Show HN: Every Day Is Pi Day by nkantar on Tuesday March 14, 2017 @11:44AM (#13868448)
As one of the comments says:

> jyssys3: The rest of the world celebrates it at 22/7.

I'd expect it's really 22.7., but this is more fun.

Re:Show HN: Every Day Is Pi Day by teekert on Tuesday March 14, 2017 @12:18PM (#13868821)
22/7 = 3.14285714285714285714 ;)