

The one second war:  Finding a lasting solution to the leap seconds problem - wgrover
http://cacm.acm.org/magazines/2011/5/107699-the-one-second-war/fulltext

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jtwb
Maybe the most awesome part of being a human being today is recycling
solutions from the past to the solutions of today.

Once upon a time, written language was represented in computers by arrays of
characters. Manipulating non-english user content in this model was big pain.
Today, effective software dealing with written language uses UTF-8 Characters
and the Grapheme abstraction. The problem was solved by separating the
concepts of Bytes, Characters and Graphemes, which were previously conflated.

Clearly, it's ineffective to use the same abstraction for "elapsed time" and
"time of day" due to the variable length of the day. Representing both
concepts with one value leads to the problems described in this article. The
concepts should be separated and a new abstraction created: Earth Position
(EP).

Statements about the time of day, day of the week or lunar month of the year
are really statements about the Earth's position relative to some other
entity: the sun in most cases, but sometimes the moon in the case of lunar
dates.

Given that "Unix time" is widely understood as "the number of seconds elapsed
since Jan 1, 1970", it would be convenient to let it only represent Elapsed
Time and define Earth Positional values in terms of Elapsed Time.

The leap second concept should only affect applications interested in Earth
Position queries (time of day, etc) and not have any representation at the
Elapsed Time level.

~~~
endian
You mean TAI vs UTC?

TAI: <http://en.wikipedia.org/wiki/International_Atomic_Time>

UTC: <http://en.wikipedia.org/wiki/Coordinated_Universal_Time>

"As of 1 January 2011, 00:00:00 UTC, TAI was exactly 34 seconds ahead of UTC"

~~~
jcr
Unfortunately, TAI (Atomic Time based on radioactive decay) may not be as
consistent as we originally thought it was according to recent observations...

[http://news.discovery.com/space/is-the-sun-emitting-a-
myster...](http://news.discovery.com/space/is-the-sun-emitting-a-mystery-
particle.html)

~~~
harshpotatoes
No. The link you gives mentions that the decay rates of radioactive particles
are changing, this saying the half life is changing. Atomic clocks are based
on the frequency of light emitted from an electronic transition. Ie, an
electron makes a transition from one state to another and emits a photon, then
we compare the frequency of that photon to another photon which has a nearby
frequency, we measure the difference to like 8 digits, then use the frequency
of the light produced from the transition as the inverrse unit of time.

One is based on nuclear decay, the other an induced electronic transition and
not affected by unknown variations in the half life.

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hugh3
Speaking as a mad scientist, it's clear to me that the best solution is just
to adjust the Earth's rotation to be exactly 24 hours.

Maybe 24 and a half, so we can all have a bit of a sleep in every morning.

~~~
uvdiv
No it should be 24.0159254 old-hours, so that the orbital period is an
integral number of earth rotations. _Assuming_ you want to waste your mad-
scientist powers on silly bureaucratic nonsense, and not on, say, spinning the
earth fast enough to lower surface gravity (leap tall buildings in a single
bound to get to Starbucks).

~~~
qntm
No, speed up the orbital period too so we can have a 360-day year.

~~~
dhimes
Quarterly reports coming sooner? No thanks. Let's slow down the orbital period
to 400 days. Nice, 100 day quarters. And, as that change leads to other
changes in our daily life, maybe I'll finally eventually use that "grad"
button on my calculator.

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dpkendal
If you live in Britain and you ever hear seven pips on BBC radio instead of
six, there's just been a leap second. That's the Greenwich Time Signal
computer compensating for the extra second.

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ars
Dup: <http://news.ycombinator.com/item?id=2418234>

~~~
wgrover
Rats, on my first submission no less! I knew this was too interesting to be
original. I'll search harder next time. Thanks for catching it.

~~~
ugh
Don't worry. I missed it the first time and enjoyed it tremendously.

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alanfalcon
I've always loved the brown M&M anecdote, and consequently it always bothers
me when it becomes a cliche sign of a diva in movies. Then again, lots of
things bother me in movies (i.e. most things here:
<http://en.wikipedia.org/wiki/List_of_common_misconceptions>).

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jarin
From my understanding, setting leap seconds 20 years in advance is not a good
idea either because large earthquakes (such as the recent one in Japan) can
change the Earth's rotation speed enough to require an update.

~~~
Deestan
According to my calculations, the Japan earthquake will not require us to
adjust a leap second - at least not within the next ~761 years.

The Japan earthquake shortened the day length by 1.8 microseconds. [1]

1.8 microseconds * 365.25 days * 20 years =~ 0.01 seconds off. Not enough to
require an update, even less an urgent update before the 20 years.

1.8 microseconds * 365.25 days * 761 years =~ 0.50 seconds off.

[1] [http://www.space.com/11115-japan-earthquake-shortened-
earth-...](http://www.space.com/11115-japan-earthquake-shortened-earth-
days.html)

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Florin_Andrei
Ignore it until it's one hour off, then do a "leap hour". We do that twice a
year anyway.

~~~
caf
PHK's argument is that leap seconds don't come frequently enough to ensure
that software is tested in their presence. Replacing them with a 3600-times
rarer event would make the problem much, much worse (but on the plus side,
it'll be our descendents' problem, not ours ;)

~~~
scotty79
I think he talks about just adjusting timezones to match.

