Math Quirks:...Anybody (else) experienced strange Date coincidences ?

[RJSV]

Of course, many many folks experience coincidences, in personal affairs, but I'm thinking, what are some interesting, unexpected, and, Engineering being a 'MATH' driven occupation, what's your cute story.
(Please refraining from offensive material, right now).

   #1.). I'll start with business address intrique, although seemingly harmless irrelevance:
    A first job, the headquarters was at '1440 Fourth Street', charming Berkeley industrial shop.
    Couple years later, (20 years), I've obtained a new job, address at:
    '1444 Market St.'  an actual play on words, a bit, if you say both addresss fast.
     Maybe not so spectacular, or dramatic, but I like the word play!

   #2.).  A certain date and number, let's just call it a 'recuring 1230', that's woven itself into several, unrelated events, including one girlfriend's birthday, and also a place I worked at, several years.
Again, perhaps more interesting to myself, than as a publicly shared 'irony'...I think it was an old friend had, also, passed on that date.

Anybody else, with a mathematical or career / business related story ?

[helius]

Do you consider it a strange coincidence that thousands of stoners celebrate by lighting up on 4/20, unaware of the corporal from Austria whose birthday is that day?

[tggzzz]

Do you consider it a strange coincidence that thousands of stoners celebrate by lighting up on 4/20, unaware of the corporal from Austria whose birthday is that day?

Strictly speaking it is the anniversary of his birthday

I suggest the OP searches the number pi, to find his date and time of birth.

Don't you find it a strange coincidence that the people who find coincidence between unrelated numbers often lived in the pre-scientific era or are astrologers/new-agers/"healers" etc?

[HighVoltage]

If you start interpreting coincidence numbers and go down that rabbit hole, it will never end.
I know some wacky people who have done that.

But on the other side you can also not avoid real coincidences.

I had to move out of a business building once and found a new place in the adjacent city and got the same street name and the house number was almost the same, just had a letter behind the number.

What I find more interesting is that test instrument companies like to use the same number combination.

For instance:
Datron 1281 is considered one of the best multimeters of all times.
I just bought a Burster calibration resistor, model number 1281

And there are plenty more examples in the lab.
One has to wonder, how that happened.







 

[Sredni]

Well, it feels like every time I pick up my phone to look at the time, it's xx:17.
 I noticed because where I live the number is considered bad luck. Of course I notice because all the other times I pick up the phone and did not get xx:17 I did not register the event. But then, out of fun, I tried to find the number 17 in combination of numbers of the clock and or date and... sure enough, a disproportionate number of times I can get 17 by either summing up the single digits, or groups of digits, or subtracting them. Like, for example, 14:21 -> 14+2+1 = 17, or 19:34 -> 9+1+3+4 = 17, 19:02 -> 19 - 2 = 17 and so on.

Since I am "almost always" able to extract 17 out of the time (sometimes with the help of the date to make it) I wonder if 17 for hours is like 7 for dices: does it have a higher probability of coming up than other numbers? Or is there a number with higher probability?

If we only consider summing all the single digits, the probability distribution function is bell shaped and spans all numbers between 0 and 24 both for the 24h and 12h formats. So, the number with the highest relative probability of coming up is 12, in both cases. Whoops, no. It's 12 in the 24h format and 11 in the 12h format.
Here are the number of occurrences for the 24h format

{{0, 1}, {1, 4}, {2, 10}, {3, 19}, {4, 31},  {5, 46}, {6, 62}, {7, 78}, {8, 93}, {9, 107},  {10, 118}, {11, 124}, {12, 125}, {13, 121},  {14, 112}, {15, 98}, {16, 82}, {17, 66}, {18, 51},  {19, 37}, {20, 25}, {21, 16}, {22, 9}, {23, 4},  {24, 1}}

and here are those for the 12h format

{{0, 1}, {1, 4}, {2, 9}, {3, 16}, {4, 24}, {5, 33},  {6, 42}, {7, 50}, {8, 57}, {9, 63}, {10, 67},  {11, 68}, {12, 66}, {13, 61}, {14, 54}, {15, 45},  {16, 36}, {17, 28}, {18, 21}, {19, 15}, {20, 10},  {21, 6}, {22, 3}, {23, 1}, {24, 0}}

But this just one of the ways of combining the digits to get a number. I could sum the first two digit and then subtract the sum of the last two, or summing the first, third and fourth and subtracting the second. How to get all the possible combinations?

[jpanhalt]

Most people are aware of the Boeing 7x7 series of aircraft:  https://simpleflying.com/boeing-7x7-series-line-up/

A "lucky number" or just a number that easily rolls off the tongue?

Now to add further intrigue, check out the author(s) of the above link and this thread?  Related in the stars?   

[igendel]

This warrants the great scene from the film Pi - excellent monologue and, towards the end, on-topic:

[ebastler]

But this just one of the ways of combining the digits to get a number. I could sum the first two digit and then subtract the sum of the last two, or summing the first, third and fourth and subtracting the second. How to get all the possible combinations?

That seems straightforward enough to answer via a little brute-force program. There are 24*60 = 1440 different hour:minute combinations. For each of these times there is a manageable number of sums you can test, if you allow yourself to either look at single digits or to combine the hours and/or minutes into two-digit numbers, and then count each of the units either as positive or negative:

2^4 = 16 single-digit sums
2^3 = 8 sums which use the hours as a two-digit number
2^3 = 8 sums which use the minutes as a two-digit number
2^2 = 4 sums which use both hours and minutes as two-digit numbers,
hence 36 combinations (which will not always produce 36 different sums).

You could easily write a program which loops through these combinations for each of the 1440 time values, to see for how many of them you can obtain 17 (or -17) as the sum. And likewise for other target sums, to see whether 17 is indeed "special".

I would be surprised if 17 happens to be the most frequently achievable sum; I think it is just your personal bias in looking at these numbers. (I assume you have not tried the other target sums when you did this manually?)

[TimFox]

Many years ago, some debated if the CDC 7600 mainframes were four times better than the ICL 1900 computers.

[Circlotron]

About 6 months ago I started seeing candy apple red Mazda 6's everywhere I went. it's like they were after me. Was at a shopping centre sitting down having a coffee with a friend and was telling him about this phenomena. After we had finished and came outside to the parking lot there was one either side of my car and a third one right behind it. 

[Sredni]

Many years ago, some debated if the CDC 7600 mainframes were four times better than the ICL 1900 computers.

I took me three re-readings to get it.
 

[Circlotron]

Many years ago, some debated if the CDC 7600 mainframes were four times better than the ICL 1900 computers.

Three times better.
Four times as good.
My pet peeve!

[TimFox]

Many years ago, some debated if the CDC 7600 mainframes were four times better than the ICL 1900 computers.

Three times better.
Four times as good.
My pet peeve!

A quick look for grammar sources indicates that "four times as good" is better usage, but "four times better" is still grammatically correct for A/B = 4:1.

[AVGresponding]

And is the equivalent of 300% better, which media sources consistently get wrong (would likely be stated to be 400% better). Yes, this annoys me as well.

[tggzzz]

And is the equivalent of 300% better, which media sources consistently get wrong (would likely be stated to be 400% better). Yes, this annoys me as well.

Worse: 2 is "10 times less" than 20.
<insert muffled sound of screaming while holding a pillow over my mouth>

[TimFox]

My standard reference book, B A Garner Garner's Modern American Usage 3rd edition, Oxford University Press 2009, discusses these usages in his entry "Illogic".
On p 440, he points out the difference between logic and grammar:  "No serious student believes anymore that grammatical distinctions necessarily reflect logical ones.", for example "burn up" vs. "burn down", or "fat chance" vs. "slim chance".
Case H on p 441 discusses "times more than", and that the common understanding is that if X = 2 and Y = 1 then X is two times more than Y.  He prefers "X is two times as much as Y", and advises against the opposite wording "Y is two times less than X", but allows "two times more than".
In my opinion, "times more than" implies a ratio.
If A = 8 watts, and B = 2 watts, then
A is 6 watts more than B.
A is four times as much as B.
A is four times more than B.
A is 6 dB more than B, parallel to the above.

In my joke, where the comparison is goodness, rather than quantity, this would read "X is two times as good as Y", which is awkward compared with "X is two times better than Y",

[helius]

On p 440, he points out the difference between logic and grammar:  "No serious student believes anymore that grammatical distinctions necessarily reflect logical ones.", for example "burn up" vs. "burn down", or "fat chance" vs. "slim chance".

If those are the examples cited, they aren't especially useful. A slim chance is a low probability, but "fat chance" is a sarcastic expression (you can tell by the vocal stress). The author seems to be blinkered by an approach to grammar that ignores the purpose and freight of the speech act itself. Expressions of sarcasm emanate from a personality and emotional state that sees the world through a gimlet eye, and can't be understood by simply reading the words' denotations or applying grammar rules. The other example is also more complicated when you include the phrases' connotations. When something burns up, we mean that it deflagrates in a more or less spontaneous way. Burning up is intransitive. Burning down, on the other hand, is mostly transitive—we impute a conscious intent to destroy or allow to be destroyed. Even when habitable structures burn down accidentally, there is a moral weight to that destruction that we don't assign with movable objects burning up (that is why fire departments were created to protect structures and not just to put out all fires). The Talking Heads song isn't called "Burning Up The House". On an over-literal level, it's true that this distinction has nothing to do with the common up-down dichotomy in terms of space, but expecting it should can only appear reasonable if the words are shorn of all their context.

Based on the quoted analysis, I think you would get more illumination from "How To Do Things With Words" by J.L. Austin.

In my opinion, "times more than" implies a ratio.
If A = 8 watts, and B = 2 watts, then
A is 6 watts more than B.
A is four times as much as B.
A is four times more than B.
A is 6 dB more than B, parallel to the above.

The inconsistencies come in when you want to substitute "four" by "one half".

[TimFox]

Garner contends that "four times less" is better avoided in English.

The discussion of "burn up" vs "burn down" is only the introduction to the discussion of logic and grammar;  point "H" in that section is directly relevant to "four times" usages and does not involve sarcasm.
"Four times more" or its variation are worth discussing since we are discussing quantities.
"Four times better" is not really mathematical:  comparing the two computers' goodness was a joke.

However, when googling "four times better", the results from periodicals such as the Guardian and the Economist have used it to compare, for example, lines of resolution in HDTV.
(I didn't link them due to paywalls.)

I seriously recommend his book, which shares my preference for discussing "standard English" and careful usage, while admitting the usefulness of non-standard English and slang for other purposes.
He found that permissive authors who encourage slang, etc. always discuss their ideas using standard English.

With respect to logic, mathematics, and grammar:  an example is the "double negative", such as "I have not done nothing."
In standard English, that is not good usage, but would mean the positive "I have done something", following Aristotle and Boole.
My Russian co-workers told me that in grammatical Russian, the equivalent sentence would be a strong negative, rather than a logical positive.

[RJSV]

   Red Mazda Conspiracy is OK, but, good thing we ARE NOT involving any meth users (Mr. White!).
That crew, for whatever reason, diagnostic 'paranoia' or psychosis maybe underlying, but those heavy meth users get the 'manic' high, combined with way, way whacky imaginative creativity and results...from a safe observing distance, results can be incredulous.  Witness that effect, in the show, Breaking Bad, making 'drama' out of simple hole digging.
"You know why,..." The shovel weilding actor addresses the (digging) action dismissively.

   (Part of my point, about coincidence tracking, is that the meth using crowd often approaches the topic from a hyper self-defensive angle, and can be dangerous and unpredictable!)

   At any rate, look;  good ole' 1440 showing up in one of the reply posts, lol.
Although my experience, involved street names also, like '4th' street.  Almost as a 'PUN', form.

[RJSV]

Sredni:
   Nice to see you've gone a bit deeper than most would...one comment I could make about frequency and statistics related.  That is, many street addresses (likely) have, statistically more numbers similar to '3569' due to simple counting, that is, some address like 9412 won't be encountered so often, as street blocks don't always go very high.  That means house address less than, say, 3000 or 4000, as the higher address values aren't there, in the city map.
Probably similar bias in any 5-digit numbers, such as 19248, which perhaps some town planners or zoning dept. know about...meaning that you maybe won't see something like 89124 as that higher number isn't seen, in the community.

[vk6zgo]

About 6 months ago I started seeing candy apple red Mazda 6's everywhere I went. it's like they were after me. Was at a shopping centre sitting down having a coffee with a friend and was telling him about this phenomena. After we had finished and came outside to the parking lot there was one either side of my car and a third one right behind it. 

Where did they find a space with all the late 1990s/early 2000s silver Toyota Camrys using them up?

[Circlotron]

About 6 months ago I started seeing candy apple red Mazda 6's everywhere I went. it's like they were after me. Was at a shopping centre sitting down having a coffee with a friend and was telling him about this phenomena. After we had finished and came outside to the parking lot there was one either side of my car and a third one right behind it. 

Where did they find a space with all the late 1990s/early 2000s silver Toyota Camrys using them up?

LOL You are so on the money.  except for the fact that my 1999 Camry is white, not silver.

[MIS42N]

The first 3 digits of my mobile and my bank account are the same. I know it's not a date coincidence. But this is:

I have four daughters (this is true, not a joke - although sometimes I wonder).
First born 30 Jan (xxxx-1-30). The second born 7 Oct (-10-7). sum the days and the months 11-37.
So what?
The third was born -7-25 and the fourth was -4-12. sum the days and the months 11-37.

My favourite is “Why do programmers always mix up Halloween and Christmas?”
“Because Oct 31 = Dec 25.”
[ Credit to the person that saw this first - Octal 31 = Decimal 25 ]

And how about this weird little calculation. I found it many years before Y2K was a thing.
Good from 1st March 1900 to 2099 if for 1900 Y=0 and for 2099 Y=199:
'
' Get date, reduce to number of days in P [1/1/1900 = 1]
'
  INPUT "Date D,M,Y"; D, M, Y: IF M < 3 THEN M = M + 12: Y = Y - 1
  P = D + INT((M+1) * 153 / 5) + INT(Y * 1461 / 4) - 63

[Nominal Animal]

For a 24-hour clock, taking either the hours or minutes as-is, and then adding or subtracting the other, or one or both digits of the other, 24.3% of the time you can end up with +17 or -17.

Bash+awk:

Code: [Select]

for H1 in 0 1 2 ; do \
  for H2 in 0 1 2 3 4 5 6 7 8 9 ; do \
    H=$[10*H1+H2] ; [ $H -ge 24 ] && continue ;\
      for M1 in 0 1 2 3 4 5 ; do \
        for M2 in 0 1 2 3 4 5 6 7 8 9 ; do \
          M=$[10*M1+M2] ;\
          printf "%d $[H*60+M]\n" $[H+M] $[H-M] $[H+M1] $[H+M2] $[H+M1+M2] $[H-M1] $[H-M2] $[H-M] $[H-M1-M2] $[H+M1-M2] $[H-M1+M2] ;\
        done ;\
      done ;\
    done ;\
  done | awk '{
                r = $1; if (r < 0) r = -r
                result[r]=r
                seen[r][$2]=1
              }
              END {
                possible=24*60
                for (r in result) {
                  n=0; for (s in seen[r]) n+=seen[r][s];
                  printf "Result %d: %d/%d = %.1f%%\n", r, n, possible, 100*n/possible
                }
              }'Even though it is brute force calculation using Bash and awk, it is still basically instantaneous.  You can paste that in any Bash shell with any variant of awk available as-is, and it will print out each possible result (in random order; append | sort -n -k 2 to the command to sort the output by the possible results), and how large a fraction of all 24-hour clocks, HH:MM, can be evaluated to that particular result.

[helius]

And how about this weird little calculation. I found it many years before Y2K was a thing.
Good from 1st March 1900 to 2099 if for 1900 Y=0 and for 2099 Y=199:

The regular cycle of days to days-of-the-week begins on March 1 because the "Ides of March" was the original start of the year.
The Julian calendar, instituted by Julius Caesar, was a revision of that earlier calendar. You can still see the traces of the ancient calendar by translating the names of months from Latin: September, October, November, December mean 7th, 8th, 9th, 10th: so the year originally began in March, with leap days inserted at the end of the year (as is done today with leap seconds).