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22-11-22 22:11:22

95 points by lun4r ↗ HN
A palindrome date, time and datetime (:

39 comments

[ 2.9 ms ] story [ 99.3 ms ] thread
coding123
I wonder if there was a single person in 1922 that had the same thought.
31337Logic
...or last year, on Nov. 12th.
quickthrower2
or 11-11-11 11:11:11

or 01-01-01 10:10:10

Interview question: write a program to list them all!

carl_dr
Sounds like a great Code Golf contest.

ruby -e 'require"date";a=DateTime.new(0,1,1,0,0,0);(0..4e9).each{|d|b=(a+Rational(d,86400));c=b.strftime("%y%m%d%H%M%S");puts b.strftime("%y-%m-%d %H:%M:%S")if c==c.reverse}'

About the most inefficient anyone could make it, but I think it works!

lcnPylGDnU4H9OF
Looks like it would be defeated by the dreaded leap second.
carl_dr
I don't think so. It would be only year 2006 (which map to second 60) which could be a problem, and there wasn't a leap year in that year.
AkshatJ27
Some saves: `Rational(d,86400)` -> `d/86400r`

Get rid of the variable `a` since it is used in only one place.

`DateTime.new(0,1,1,0,0,0)` -> `DateTime.new(0,1,1)`

also in newer ruby versions you can use numbered parameters to replace d with _1 and remove `|d|`

Pretty sure there might be some more which i do not see immediately :)

carl_dr
ruby -e 'require"date";(0..4e9).each{b=DateTime.new(0,1,1)+_1/86400r;c=b.strftime("%y%m%d%H%M%S");puts b.strftime("%y-%m-%d %H:%M:%S")if c==c.reverse}'

151 bytes (including the ruby -e, down from 174.) Thanks!

AkshatJ27
`ruby -e 'require"date";0.upto(4e9){b=DateTime.new(0,1,1)+_1/86400r;c=b.strftime"%y%m%d%H%M%S";p b.strftime"%y-%m-%d %H:%M:%S"if c==c.reverse}'`

142? Sorry if I broke anything, on phone.

carl_dr
You need to use puts to avoid quotes being added around the output - so I'll give you 145! I'm on my phone too, I'm impressed I even got something working, you've done brilliantly.

Edit: DateTime.new(0) seems to work. 141.

AkshatJ27
~~`b=DateTime.new(0,1,1)+_1/86400r;`-> `b=_1/86400r+DateTime.new 0`~~ oops
carl_dr
That doesn't work unfortunately, you need the brackets - DateTime has to be on the left.
AkshatJ27
ah, my bad.

This should work for 134:

`ruby -r date -e '0.upto(4e9){b=DateTime.new(0)+_1/86400r;puts b.strftime"%y-%m-%d %H:%M:%S"if(c=b.strftime"%y%m%d%H%M%S")==c.reverse}'`

carl_dr
ruby -rdate -e'b=DateTime.new 0;loop{b+=1/86400r;c=b.strftime"%y%m%d%H%M%S";puts b.strftime"%y-%m-%d %H:%M:%S"if c==c.reverse}'

127. Script never terminates, but it does display all possibilities, so I think it still passes!

Edit: 126. ruby -rdate -e'b=DateTime.new 0;loop{b+=1/86400r;puts b.strftime"%y-%m-%d %H:%M:%S"if(c=b.strftime"%y%m%d%H%M%S")==c.reverse}'

I think I'm done for the moment, will revisit tomorrow if you can find any further savings!

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PinkMilkshake
PowerShell 7, 108 chars

  0..2e9|%{date(date 0).AddSeconds($_)-f 'yy-MM-dd HH:mm:ss'}|?{$_-match'(.)(.)-(.)(.)-(.)(.) \6\5:\4\3:\2\1'}
yamtaddle
> write a program to list them all!

Me: Is it OK if it doesn't print until it's done?

Interviewer: Uh, sure, why not?

Me: while(1){}

Me: Finished. This produces the exact desired output of the program you specified.

Interviewer: GTFO.

quickthrower2
while(1) {} is the universal program to do anything. You can then optimise performance later.

Interestingly in Haskell the only pure program of type variable “a” where a means any type at all is the one that never quits:

    myProg: a

    myProg = myProg
Which amounts to the same thing: it can do anything - produce any type - but it takes literally forever.
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bproctor
I still regret missing Michael Scott's 05-05-05 party. It only happens once every billion years.
aidenn0
Surely every 100 years?
chungy
He was quoting Michael Scott.
aidenn0
I had to google "Michael Scott" I'm guessing it's from The Office not the ex-CEO of Apple.
Ekaros
It could happen pretty often. Just need to start enough calendars.
timeaway
Unix time 1666666666 happened last month, on October 25th 02:57:46 UTC.

A closer "round" number will be 1670000000, happening next month on December 2nd 16:53:20 UTC.

But for 1700000000 we'll have to wait until next year, November 14th 22:13:20 2023 UTC.

ASalazarMX
1666666666 was special, though. A beast of a number, no, three beasts of a number.
a9h74j
Am I correct that the 32nd prime is 1,453,168,141, and the 33rd prime is 2,300,942,549?

I've noticed good times like that getting fewer and farther between.

DrNosferatu
Just realized that on 22-11–22, 22:11:22 I had exactly 212 HN karma points - surely the Universe is trying to say something…
sillysaurusx
Now the question is, would you like to be downvoted to maintain stasis, or try to get to 2112 karma before tomorrow? :)
senectus1
yup, you've hit your peak. it's all downhill from here :-D
DrNosferatu
Oh My Golly, guys - it was the announcement of the Coming of chatGPT!
kristianp
Where I am it's currently Fibonacci day: 11/23