
2016 will be one second longer - upen
http://sciencebulletin.org/archives/2912.html
======
brudgers
Personally, a leap hour seems about the right level of granularity, but I
suppose an approximately once per century leap minute would be ok. But leap
seconds are a waste of time.

If ignored since their introduction in 1972, official time would be out of
sync with the Earth's rotation by 26 seconds. There's been a lot of running
around and gnashing of teeth to correct 1.845668179868485e-7 error that isn't
even an error most of the time. The 26 seconds of error fleshes out as 7.389
meters at the equator when using celestial navigation and for anything that
accurate we use radio signals not a sextant.

The Earth's rotation and revolution are useful abstractions at a certain level
of granularity. But the reason we have atomic clocks is because those
abstractions break down when we need precise measurements of reality. Reality
is real because the rotation and revolution of the Earth are not cosmological
constants. Leap seconds are an expression of the superstition that humans
control the arrow of time: as if one thing happening after another would cease
to be the case without them.

~~~
frisco
An error of 7 meters would probably mean the FAA would refuse to certify GPS
for aircraft use. Even now it's only usable in many circumstances with ground
based corrections (eg WAAS or GBAS). A minute of error would probably make it
unusable for enroute navigation.

~~~
creeble
I'm sure someone will point it out, but GPS doesn't use leap seconds.

"Adding leap seconds is a waste of time" I see what you did there. And agree!

~~~
frisco
Interesting. I didn't know that. I think half of the point remains (what
sounds like a small error can be critical) but I guess GPS isn't a great
example, then, as safety critical systems tend to be smarter by design anyway.

~~~
brudgers
The safety critical systems don't reset their clocks because safety critical
systems maintain independence in order to maintain safety. Safety critical
systems are a place where the abstraction of a Terran Year as a cosmological
constant breaks down.

------
creeble
A small point I missed that is covered in this article: leap seconds aren't
added just because of the slowing of the Earth's rotation (as I've always
explained it to others), but because atomic time is a few milliseconds per day
faster than Earth time in general.

Not sure how I missed that in previous discussions of leap seconds, but now I
can comfortably spend my leap second in 2016 basking in this knowledge.

~~~
arikrak
Why couldn't they define the leap second more precisely then? I think there
has to be an astronomic reason for the leap second. Either the Earth is
slowing down or maybe the they want better alignment between the earth daily
rotation and annual revolution.

~~~
creeble
It's both: average inaccuracy, and adjusted earth spin.

------
TorKlingberg
Oh, so I can annoy my friends by counting down to the new year "correctly",
one second after them.

~~~
joeax
Your phone should update at one second before midnight UTC. So if your in EST
then at 6:59:59, watch for 59 to be counted twice.

~~~
gshubert17
I believe 6:59:59 will be followed by 6:59:60. See the screen shot I took of a
leap second added in 2008.

[https://www.flickr.com/photos/127045916@N06/31678955582/](https://www.flickr.com/photos/127045916@N06/31678955582/)

~~~
devy
Yep. The extra second is the 60th second. [http://earthsky.org/human-
world/leap-second-june-30-december...](http://earthsky.org/human-world/leap-
second-june-30-december-31-why-need-controversy)

------
seagreen
Leap seconds have no business being tracked in the core logic of our programs.

Just like timezones and calendar changes, leap seconds are a display issue.
While obviously very important in some circumstances there's no need to keep
track of them through absolutely all of our code.

If the way you measure time takes leap seconds into account, you have no way
of saying "exactly X Système international seconds from now". This is a big
deal.

~~~
rspeer
> If the way you measure time takes leap seconds into account, you have no way
> of saying "exactly X Système international seconds from now".

Note that this is the case for anyone using POSIX time, which inherently
assumes that hours start on multiples of 3600, and has to be adjusted or
smeared when a leap second happens.

But I've never seen a system that follows your recommendation, using TAI as
the internal time and something like TAI-5:00:36 as the local time, except for
GPS devices.

------
_greim_
Question for the experts. Say I'm writing a bunch of code for date/time stuff
in JavaScript, using the built-in `Date` API. Is this something I need to
worry about? I've read countless "falsehoods programmers believe about time"
blog posts but they tend to not explain the _why_ of it.

~~~
brudgers
I'm making to no claim to being an expert. Nevertheless, my question is "Does
one second matter to your application? If so, how does Javascript's single
threading, garbage collection, and default asynchronous programming idioms fit
with the needs of a real or near real time system?"

~~~
_greim_
> Does one second matter to your application?

Yes. And it's not just real-time; even when just displaying dates and times,
an off-by-one error at any granularity can bump it into the next year.

I guess what I'm wondering is how does the decision to add a leap second here
or there find its way into system clocks, such that it knows whether:

    
    
        new Date(1483228800000).getUTCFullYear()
    

...is 2016 or 2017?

~~~
rspeer
JavaScript timestamps are POSIX timestamps times 1000, and POSIX timestamps
have to be corrected for leap seconds at the OS level, not in the application.

The advantage of this is that 1483228800000 is definitely the start of 2017
(and in general, UTC days start on multiples of 86400 seconds, or 86400000 in
JS). The disadvantage is that Date(1483228799999) could happen twice, and the
first time it would be followed by Date(1483228799000).

In your application, you have to be able to cope with time going backwards for
a moment. (But this is already true whenever your system contacts an NTP
server.)

------
an_account
10... 9... 8... 7... 6... 5... 4... 3... 2... 1... 1... 0!!!

~~~
halomru
The seconds count 23:55 56 57 58 59 60 00:00

Counting the leap second twice is more of a quick hack used in computers, but
it's not how it actually works

------
Applejinx
You know, if I had to pick a year to have one extra second of, 2016 would be
pretty much be last on the list.

Everybody brace yourselves for that second, lest another cool person die! :P

~~~
iamatworknow
I hope you're saying this in jest, but even then the meme that "2016 has been
the worst!" has been pretty insufferable. It's usually used in the context of
celebrity deaths, but think about the explosion of mass media that occurred
between the 70's and today.

With more TV channels, radio stations, and the internet, the number of public
figures we're exposed to on a regular basis is far greater than any generation
before us. And like all of us those people die, and will keep dying, and the
half-hearted and self-centered social media mourning will become even more
commonplace.

I, for one, can accept celebrity deaths, but I'm not sure if I can accept the
annoying cultural impact they seem to be having.

~~~
CorvusCrypto
It's not just about the deaths, but also about the social and political events
that have occurred. It can be argued that this has happened before at this
frequency also and mass media is the culprit, but if the cultural impact is
more awareness we should applaud it, not shy away. Annoying as they are,
social media and memes offer a way to connect many to an idea and make things
a bit more light-hearted as well.

~~~
iamatworknow
My frustration is more with the reaction to celebrity deaths where people use
the death as a means to focus attention on themselves, and how a lot of people
seem to think that a magic cosmic switch will turn off on December 31 and
they'll stop happening.

------
starquake
I'm curious to see it the countdown on TV is going to take this into account

~~~
takeda
Unfortunately (I would like to see it too), it only needs to be included if
you're in UTC time zone, everywhere else the countdown will be the same.

------
wglb
When I was a young ham radio operator, I would listen to WWV often, both for
time and propagation. I ordered a publication
[http://tf.nist.gov/general/pdf/1788.pdf](http://tf.nist.gov/general/pdf/1788.pdf)
which has just about my favorite title for an article _Dating of Events in the
Vicinity of Leap Seconds_. More modern material is at
[https://www.nist.gov/pml/time-and-frequency-division/leap-
se...](https://www.nist.gov/pml/time-and-frequency-division/leap-seconds-
faqs).

A good resource for red hat linux is
[https://access.redhat.com/articles/15145](https://access.redhat.com/articles/15145).
And another resource is [https://ics-cert.us-
cert.gov/sites/default/files/documents/B...](https://ics-cert.us-
cert.gov/sites/default/files/documents/Best_Practices_for_Leap_Second_Event_Occurring_on_31_December_2016_S508C.pdf)

------
jasongill
Hasn't this been discussed ad nauseam on HN before? The leap second insertion
was announced 6 months ago

~~~
PedroBatista
Yes! and has been in everyone's mind ever since!

------
hiccup
Finally, the time I need to get that side project done. Show HN: Passive
Income 2017 post, here I come!!!

------
chomp
Yep, set my NTP server to slew the leap second after getting wrecked by the
last one!

~~~
snuxoll
I always found this a fascinating way to deal with the problem of leap
seconds. I've been tempted to switch my servers from UTC to TAI to avoid the
leap seconds altogether but I've been coming to realize that the clock being
out of drift is more likely to confuse my coworkers than "just" dealing with a
non-local time offset. Maybe I'll do this myself before the end of the year -
but who am I kidding, I don't have time to reconfigure my NTP server right
now.

------
matt_wulfeck
Good reminder to use Google's public ntp servers, which perform leap-second
smearing[1]. This is the only sensical way to handle this without strange edge
cases in every-day software.

1\. [https://developers.google.com/time/](https://developers.google.com/time/)

------
finid
One second!

In real terms, does it really count?

A few months back, a friend of mine was so happy when she got on a scale and
found that she's lost one pound. One pound!

~~~
tonmoy
At least in the technical would I suppose it's a lot. For example your GPS
could be off by miles because of 1 second.

~~~
lucb1e
Being off by a millisecond is already too much for practical use, if I recall
correctly.

GPS needs something more precise anyway, it's not for these systems that we
need to include whole-second corrections. And besides, GPS doesn't actually
use leap seconds.

------
xg15
That moment when some horrible thing will happen in that last second...

------
masmullin
10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 1, Happy New YEAR!!!

~~~
CorvusCrypto
Another damn off-by-one error :(

~~~
masmullin
LOL

10,9,8,7,6,5,4,3,2,1,[Insert Shell Code]

/root/ #:

~~~
sirn
What will you do when you gain root access to the spacetime shell?

(Sorry, drunk)

~~~
kobeya
Delete entropy.

------
analog31
My band will have to play auld lang syne in five.

------
li4ick
Just to give time to somebody else to die.

------
filipn
Haven't we suffered enough..

------
Somasis
Let it end.

