Today, in myths!
 

Today, in math!

The challenge: take all three parts of today's date (day, month, and year, 2 or 4 digit) and subject them to some [U][B]simple[/B][/U] math to get an interesting result or make some interesting observation about a standard representation of the date.

Is intended to be a one post a day thread. The first person to post on a date (during that date in their locale) is it, no one-ups-manship.

A couple of examples:

A few days ago it was November 21st, 2012.
Written YYMMDD it was 121121, a palindrome.

Today was/is November 27th, 2012.
YY+MM+DD is 12+11+27=50 that is a nice round number.

For today's date, if I form MMDDYYYY into a valid 7-digit IMDB movie index by retaining the last 3 digits of the year, I get 1127012, which yields a rather [url=http://www.imdb.com/title/tt0121127/]titillating[/url] title. Anyone have a copy of this classic in their collection?

Trying the same experiment with YYYMMDD format yields what appears to be a Bollywood song-and-dance thang, cannot tell if it was a hit or a 'bust' at the box office.

Today is my birthday. I was born in 19xx. My age is: xx div 2

Happy b'day!
Today is a prime... if you write it viceversa (21028211)...

[QUOTE=ATH;319803]Today is my birthday. I was born in 19xx. My age is: xx div 2[/QUOTE]

Happy 2kth birthday to you! :party:

[QUOTE=LaurV;319804]Happy b'day!
Today is a prime... if you write it viceversa (21028211)...[/QUOTE]

And the digit sum is prime as well.

[QUOTE=ATH;319803]Today is my birthday. I was born in 19[B]75[/B]. My age is: [B]75[/B] div 2 [B]= 37[/B].[/QUOTE]

Happy Birthday! :smile:

[QUOTE=jnml;319806]Happy 2kth birthday to you![/QUOTE]

Oh sh..! :smile: See [URL="http://www.mersenneforum.org/showpost.php?p=319920&postcount=7"]#7[/URL]

[QUOTE=Uncwilly;319785]Is intended to be a one post a day thread. The first person to post on a date (during that date in their locale) is it, no one-ups-manship.[/QUOTE]For today 12 - (12 - 2) = 2 the only even prime.

Today 31/12/2012 is the last day to not have unique digits in the year (since 31/12/1987).

[QUOTE=Uncwilly;323255]Today 31/12/2012 is the last day to not have unique digits in the year (since 31/12/1987).[/QUOTE]Until 2020 presumably.

[CODE]13 <- year is prime
-1 <-take away month
-1 <-take away day
-------------------
11 <- prime
[/CODE]

mulltiply year by day and divide by month, we still are in the same year!

2013 is one of the rare years whose Gregorian year number has "0", "1", "2", and "3".

Next one will be 2031, then no more until 2103.

[QUOTE=cheesehead;323429]2013 is one of the rare years whose Gregorian year number has "0", "1", "2", and "3".[/QUOTE]
And today added a "4" in the date.

Today's date: 5/1/13 (Euro style)
5=1+1+3

[CODE] 20 <-century
-13 <-years
- 1 <-month
---------------
6 <-day[/CODE]

(2013[sup]2[/sup]-911)/2 is prime.

((2013[sup]61[/sup]-1)/2012)-61 is divisible by 503 (a factor of 2012).

(20-13)/7=1

2+0+1+3+1=7

Today is (over here) 1/8/13, and (1+1)^3 = 8.

Over there, it's 8/1/13, so 8 = (1+1)^3.

oh well, this one is too good to ignore, even a day late

yesterday: 1/12/13

11213 is the smallest five digit Mersenne prime exponent

[QUOTE=davar55;324573]yesterday: 1/12/13

11213 is the smallest five digit Mersenne prime exponent[/QUOTE]
Yesterday was a busy day for me, but I was going to post:

1+12=13

[QUOTE=Uncwilly;324577]Yesterday was a busy day for me, but I was going to post:

1+12=13[/QUOTE]Equivalently, 12+1=13 in little-endian format.



Today, 13*1 = 1*13=13

[TEX]\frac{13}{13}=1[/TEX]

(13-14)+2-0 = 1

Since we're only allowed one entry here per day,
with one-ups-manship to be avoided, I'll leave unnoticed
the fact that

21+3 = (1+1),4 + 0

where , is concatenation.

Today has been:
13131 = YYMDD
or
31113 = DDMYY

both palindromes.

[QUOTE=ATH;319803]Today is my birthday. I was born in 19xx. My age is: xx div 2[/QUOTE]

Not possible on November 28th, 2012.

Your birth year would have to be 1974-2/3rds and your age would have to be 37-1/3rd. But if your age was 37-1/3rd, it would not be your birthday.

...or if your birth year was 1975, your age would be 75 / 2 = 37.5...once again it wouldn't be your birthday.

:-)

1213
1321
2113
20113
130201
are all prime :smile:

[QUOTE=gd_barnes;327005]Not possible on November 28th, 2012.

Your birth year would have to be 1974-2/3rds and your age would have to be 37-1/3rd. But if your age was 37-1/3rd, it would not be your birthday.

...or if your birth year was 1975, your age would be 75 / 2 = 37.5...once again it wouldn't be your birthday.

:-)[/QUOTE]

"Div" is integer division, smartass :mad:

75 div 2 = 37

[QUOTE=axn;327008]"Div" is integer division, smartass :mad:

75 div 2 = 37[/QUOTE]

Nice name calling.

It depends on the audience. If you're not a programmer, which 90+% of the population and likely 50+% of this forum is not, div is just short for divided by. :smile:

Today 13, 2, 1
1321 is prime

div is, where I come from, a divergence operator on a [FONT=CMR12]differentiable vector field.[/FONT]
[FONT=CMR12]The results is a [FONT=CMR12]scalar field.[/FONT]
[/FONT]

[QUOTE=Batalov;327135]div is, where I come from, a divergence operator on a [FONT=CMR12]differentiable vector field.[/FONT]
[FONT=CMR12]The results is a [FONT=CMR12]scalar field.[/FONT]
[/FONT][/QUOTE]

Or more generally, it acts on a rank n tensor and returns a rank n-1 tensor :smile:

Here in Europe we write today's date as 11/2/13.

11213 is the exponent of the 23rd Mersenne Prime.

[QUOTE=Brian-E;328953]Here in Europe we write today's date as 11/2/13.

11213 is the exponent of the 23rd Mersenne Prime.[/QUOTE]
The best post in the thread until now! :tu:

The date 1/12/13 American style was posted one day late,
so we concede to the previous poster.

How long until the next perfectly Mersenne date ...?

[QUOTE=Brian-E;328953]Here in Europe we write today's date as 11/2/13.[/QUOTE]

Wouldn't it be more logical to give all dates in YYYYMMDD format?

At least, for the next 8936 years?

[QUOTE=davar55;328987]The date 1/12/13 American style was posted one day late,
so we concede to the previous poster.[/QUOTE]
Oh! I missed your post about that date completely. You were first.
The number 11213 was actually in my mind because Hendrik Lenstra mentioned the number as his "favourite prime number" on a television show here a few days ago in which they were discussing GIMPS' new Mersenne Prime discovery. He said it was his favourite because it is the exponent of what was the largest known Mersenne Prime at the time when he was first studying number theory. He didn't note anything about today's date or January 12, though, and it was only when I had to write the date on something today that I made the connection.

[QUOTE=chalsall;328989]Wouldn't it be more logical to give all dates in YYYYMMDD format?

At least, for the next 8936 years?[/QUOTE]
Yes, I prefer that method too. It makes ordering dates much simpler. But I think we need to allow some slack with writing dates if we're going to get much inspiration for this thread.:smile:

[QUOTE=Brian-E;328993]Yes, I prefer that method too. It makes ordering dates much simpler. But I think we need to allow some slack with writing dates if we're going to get much inspiration for this thread.:smile:[/QUOTE]

Let me then present this...

This next Valentine's day is going to be 2013.02.14.

Or, 14.02.13. Or 14.13.02. Or 13.14.02. Or 13.02.14...

The populous questioned the "year 2000 bug" where Cobol programmers had to "fix" the code where the year was only two digits. And billions of dollars were spent to prevent an error.

Strangely, the humans who complained are still only using two digits for the year....

That's because we "know what we mean". Computers don't. (It's one of the few differences left between true intelligence and raw computational power. Like the infamous "DWIMNWIS" Perl module.)

[QUOTE=Dubslow;328998]That's because we "know what we mean". Computers don't. (It's one of the few differences left between true intelligence and raw computational power. Like the infamous "DWIMNWIS" Perl module.)[/QUOTE]

The transmitter has a great deal of responsibility to ensure the message is received correctly.

The receiver has the most work to do.

As an aside, Shannon was only dealing with deterministic systems and messages through noisy channels.

[QUOTE=chalsall;328997]Let me then present this...

This next Valentine's day is going to be 2013.02.14.

Or, 14.02.13. Or 14.13.02. Or 13.14.02. Or 13.02.14...
[/QUOTE]

I am more connected to 2013.02.13, it being the day I was born.....and on a Friday, no less.

lets change the title to
Meth, not even once (today)

[QUOTE=kladner;329019]I am more connected to 2013.02.13, it being the day I was born.....and on a Friday, no less.[/QUOTE]

You were born in the future?

[QUOTE=chalsall;329028]You were born in the future?[/QUOTE]

Oops! I knew I'd slip up and get caught sooner or later. Doh!:doh!:

[QUOTE=kladner;329032]Oops! I knew I'd slip up and get caught sooner or later. Doh!:doh!:[/QUOTE]

Don't sweat it. It's a common mistake.

Everyone has only one birth day. The rest are simply anniversaries. :smile:

[LEFT][SIZE=1][COLOR=LightBlue]I'd better sneak back to the future before anyone else notices.[/COLOR][/SIZE]
[/LEFT]

Today (American style):
3/1/13 = 3113
or
13/3/1 = 1331

:skiing:
Go Hang a Salami! I'm a Lasagna Hog!
:chalsall:

Is "meth" what you Yanks call meths?

Assembling all of the early primes from today's date:

2 = day
3 = month
5 = 3 + 2 = day + month
7 = 13 - ( 3 * 2 ) = year - ( month * day )
11 = 13 - 2 = year - day
13 = year

:alien2:

:smile:

If you subscribe to the date system that is used by all the cool kids you will know that today is:
3/11/13 -> 31113
31113 is a palindrome that has factors of:
3[SUP]2[/SUP] × [I]3457[/I] :smile:

[QUOTE=Uncwilly;332902]If you subscribe to the date system that is used by all the cool kids you will know that today is:
3/11/13 -> 31113 [/QUOTE]

Meanwhile... All the [I]really[/I] cool kids know that today is 20130311....

Edit: 1709 * 11779.

[QUOTE=chalsall;332903]Meanwhile... All the [I]really[/I] cool kids know that today is 20130311....[/QUOTE]How is that string of numbers significant?

[QUOTE=Uncwilly;332904]How is that string of numbers significant?[/QUOTE]

Because you can sort on it.

And the date string will be valid for the next 7977 years.

[QUOTE=Uncwilly;332904]How is that string of numbers significant?[/QUOTE]

If you want to get anal, tomorrow will be 20130312, which is 2^3 * 3 * 17 * 49339.

[QUOTE=chalsall;332909]Because you can sort on it.

[B]And the date string will be valid for the next [U][I]7977[/I][/U] years.[/B][/QUOTE]
Might I inquire why it won't be valid for the next [B]7986[/B] years?

[QUOTE=davieddy;331658]Is "meth" what you Yanks call meths?[/QUOTE]

Do speakers of British English actually refer to methamphetamines as "meths"? I suppose it would make sense given the whole "maths" thing, but I had never thought about it...

(edit crosspost, I was referring to 7986 years above)
:rofl: I realized [U]after[/U] I read chalsall's edit, first I did not even think to compute it, I took it as correct, but then when I read the edit I computed in my mind and few years were missing. The mistake is more hilarious because of that edit :smile:.

[QUOTE=NBtarheel_33;332922]Do speakers of British English actually refer to methamphetamines as "meths"? I suppose it would make sense given the whole "maths" thing, but I had never thought about it...[/QUOTE]

No, this is what we British refer to as 'meths'

[URL]http://en.wikipedia.org/wiki/Denatured_alcohol[/URL]

[url]http://xkcd.com/1179/[/url]

Today has been:
3/13/13 -> 31313 a palindrome
or
13313 a prime

We all win!
:party:

:beer:HAPPY (MERRY?) PI DAY!!! 3/14/13 - along with many other interesting calendar occurrences, we now have the honor of witnessing the once-a-century Palindromic Pi Day! :smile: :toot::beer:

You know what they say...only a real *square* forgets Pi Day!

[QUOTE=NBtarheel_33;333282]:beer:HAPPY (MERRY?) PI DAY!!! 3/14/13 - along with many other interesting calendar occurrences, we now have the honor of witnessing the once-a-century Palindromic Pi Day! :smile: :toot::beer:

You know what they say...only a real *square* forgets Pi Day![/QUOTE]

it is a square (3+14)-13 = 4

[QUOTE=NBtarheel_33;333282]:beer:HAPPY (MERRY?) PI DAY!!! 3/14/13 - along with many other interesting calendar occurrences, we now have the honor of witnessing the once-a-century Palindromic Pi Day! :smile: :toot::beer:[/QUOTE]I noted the passing of 1:59:26 local time.

Today has been "Pi Day the Thirteenth".:raccoon:

Today's date 4/5/2013 (or 5/4/2013 or 2013/4/5) backwards sorted is

543210

This is the first such "countdown" occurrence this millenium.

[QUOTE=davar55;336166]Today's date 4/5/2013 (or 5/4/2013 or 2013/4/5) backwards sorted is

543210

This is the first such "countdown" occurrence this millenium.[/QUOTE]

16/5/2034 (or 5/16/2034 or 2034/5/16) will be the first one with 7 digits.

9/4/13 or 4/9/13
9+4=13
Both the month and day are squares of primes.

MAY DAY
MAY DAY
MAY DAY

What a lovely May Day it has been.

5/1/13
5 = 1 + 1 + 3
5 = 5

2013/1/5
2 + 0 + 1 + 3 - 1 = 5
or
2 + 0 + 1 + 3 = 1 + 5

[QUOTE=davar55;336166]Today's date 4/5/2013 (or 5/4/2013 or 2013/4/5) backwards sorted is

543210

This is the first such "countdown" occurrence this millenium.[/QUOTE]

[QUOTE=ATH;336277]16/5/2034 (or 5/16/2034 or 2034/5/16) will be the first one with 7 digits.[/QUOTE]

Today's date (May 4, 2013) has the same "countdown" property.

[QUOTE=davar55;339234]Today's date (May 4, 2013) has the same "countdown" property.[/QUOTE]

May the fourth be with you.

And how about a fresh quart of mayo for Quatro de Mayo.

5/5/2013 -> (5-5)+2+0+1+3 = 0+2+1+3 = 6 = a perfect number.

Idle Polish (notation) chit-chat
 

May 6, 2013 (5/6/2013 here in the USA), and using postfix notation just because it makes this look that much more elegant (yay postfix!):

2013*++ = 5
2013*+* = 6

May 8, 2013: 5+8 = 8+5 = 13. (Some days are more interesting than others...)

5/9/13 = an arithmetic progression

(as was said, some days are just less interesting)

month divides ((2^day)-(year)) today

edit: this property is way too common it seems about 18 times after January in 2013 alone.

Ok, so today is 5 11 2013
my first thought is

5 + 11 - 2 is almost 13

5/12/13

Pythagorus Day !

5[sup]2[/sup] + 12[sup]2[/sup] = 13[sup]2[/sup]

Just peachy keen !

Only 2 dates in 2013 will be prime numbers in all 3 internationally used formats:

YYYYMMDD / DDMMYYYY / MMDDYYYY

[URL="http://en.wikipedia.org/wiki/Date_format_by_country#Map"]http://en.wikipedia.org/wiki/Date_format_by_country#Map[/URL]

May 27th 2013: 20130527, 27052013 and 05272013 are primes
Dec 7th 2013: 20131207, 07122013 and 12072013 are primes

Next time will be 2017 with 4 dates (Feb 23rd, May 11th, Sep 3rd, Nov 1st)



If 2 digit year format is used: YYMMDD / DDMMYY / MMDDYY, there are 5 dates in 2013: Jan 21st, Mar 3rd, Mar 7th, Nov 29th, Dec 13th.
(and 4 in 2017: Feb 27th, June 9th, July 7th, Oct 23rd)

8/20/2013

Today is Tuesday The Twentieth Two Thousand Thirteen

[QUOTE=davar55;350208]8/20/2013

Today is Tuesday The Twentieth Two Thousand Thirteen[/QUOTE]

Alliteration And Assonance Add Auspicious Awesomeness At All Amazing August Annunciations! ARGH And Avast! :chappy:

9/11/13: three successive odd numbers.

Oog ... missed that. 11/12/13 soon.

24/09/2013

24 = 0+9+2+0+13

and so it goes ...

[QUOTE=cheesehead;353047]Oog ... missed that. 11/12/13 soon.[/QUOTE]

Don't forget 11/12/13 @ 14:15:16

?
 

error 999

please excuse and delete

Today is still 10/1/2013.

10 + 1 + 2 = 0 + 13.

And so it goes.

Today is 11 / 12 / 13. Only 1 (3) more consecutive date combos left in this century.

Today is 12 / 03 / 2013.

That's 1203 2013.

Same digits. All four. Consecutive.

I must have too much time on my hands.

:smile:

I had been reminding myself to post on the first of December, looks like I still forgot in the end...

1/12/13 --> 11213 is the exponent of M23! Although I prefer to write the date by year,month,day anyway, because it makes more sense that way around.

Ah well....

[QUOTE=davar55;324573]oh well, this one is too good to ignore, even a day late

yesterday: 1/12/13

11213 is the smallest five digit Mersenne prime exponent[/QUOTE]

[QUOTE=Brian-E;328953]Here in Europe we write today's date as 11/2/13.

11213 is the exponent of the 23rd Mersenne Prime.[/QUOTE]

[QUOTE=blahpy;361448]I had been reminding myself to post on the first of December, looks like I still forgot in the end...

1/12/13 --> 11213 is the exponent of M23! Although I prefer to write the date by year,month,day anyway, because it makes more sense that way around.

Ah well....[/QUOTE]
For the third and last time noted for this exponent!

As far as I can tell we have to wait for February 3 / March 2, 2017, for the next such date.

As predicted about a month ago,
today's date, 11/12/13, in dd/mm/yy order,
consists of three consecutive integers.

Namely 11, 12, and 13.

This doesn't happen very often. (Homework problem)

I do have too much time on my hands.

BTW I missed the timestamp 14:15:16, but only by
a few hours. Time flies ...

Year + month = day
13 + 12 = 25

Today in myths:

It is not actually Jesus Christ's birth day today.

Am I doing this right?

Don't think so.

25/12/2013

( Day - Month ) MOD 100 = Year MOD 100 = 13,

which coincidentally is how many drinks I plan to consume today ;)

I was born on 02/13/1976. Note, 2*13=26, 26*76=1976 :smile: