F-ckin Leap Seconds, how do they work?

George Herbert george.herbert at gmail.com
Wed Jul 4 03:15:42 UTC 2012

On Tue, Jul 3, 2012 at 4:48 PM, Owen DeLong <owen at delong.com> wrote:
> Most people operate on the assumption that there are 86400*365.25 seconds per year overall and that every day is 86,400 seconds. UTC matches that common conception of time. UT1 does not because UT1 monotonically increments one second for every elapsed second of time and continues to drift out of synchronization with the celestial phenomena on which the common conception of time is based.

Let's be clear - the "celestial phenomena" vary regularly.  The Sun
and Moon do not rise and set at the same exact time every day; people
would not practically notice a second-a-year skew in this for decades
or longer, much less societally have grounds to object to it.  And
it's only historically been about 0.625 s / yr averaged since 1972.
At that long term rate (if that's what it ended up being) it would be
about a minute a century, or 6000 years before we saw things happening
a whole hour off from "expected solar time", which to be frank stops
being meaningful around when you have real clocks and astronomy.

The only people for which the celestial phenomena timing matters this
precisely are astronomers, who ALREADY have to do their own things to
keep everything straight, much more precisely than the leap seconds
correct the ongoing skews.

This (irregular leap seconds) is a solution which is monumentally
badly matched to the actual problem set.

>> NTP can keep time in UTC (or anything else) if it wants, but it should discipline the system clock to monotonically increasing UT1.
> This will break many many currently correct applications and is not a change that should be undertaken lightly. Especially not if it is intended to fix a moderately esoteric bug in a few things that crops up once per decade or so.

I would argue exactly the opposite.  It's unpredictable and irregular
enough that a nearly completely new set of software and administrators
are what encounters it each time it comes through.  It broke chunks of
the internet this time.  Last time, this was a "Oh, well, some geeks
inconvenienced, shrug".  This time it was fortunately small enough
(esp. in comparison to the recent AWS outage due to more malign
natural forces) that it wasn't a big deal.  It could be more
disruptive next time.

>From an Internet Stability point of view, one can easily take the
position that This Just Does Not Do.

So - It's there to keep us in sync with the stars, except it's done in
increments nobody will notice but astronomers, who have to do better
than that anyways; it disrupts technology, to a mild to moderate
degree.  Why are we doing it again?

I like this atomic time thing.  It's sounding better and better each
day we keep arguing about it.  If it bothers you that much we can
schedule in a leap hour for Y8000 (or, Y5000, Y11000, Y17000, ....).

It's not a butthead thing to do to assert that the Internet's
stability in this matter now outweighs an arbitrary and abstract
argument among timekeepers.  We matter more than they do, now.  If
they want to keep a more true Solar Time they can do so; we can run on
atomic and put this silly notion of trying to say Sun-centric behind
us.  This is the 21st century.

Leapsecondo Delenda Est!

-george william herbert
george.herbert at gmail.com

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