F-ckin Leap Seconds, how do they work?

Nick Hilliard nick at foobar.org
Tue Jul 3 18:33:05 UTC 2012


On 03/07/2012 18:59, Saku Ytti wrote:
> Leap bugs are NOT known. Most people have no idea unixtime is not
> monotonically increasing.
> I had no idea myself until sunday, I had assumed we really go 59 -> 60 ->
> 00, but we go 59 -> 59 -> 00. So 59.1 can happen before or after 59.2.
> To me this is fundamentally and inherently broken.

Well, yeah, it's not obvious that a minute can have anywhere between 59 and
62 seconds.  Certainly if POSIX were being redesigned, they ought to
consider using libtai.

Google's approach to this is interesting:

> http://googleblog.blogspot.ie/2011/09/time-technology-and-leaping-seconds.html

i.e. controlled clock slew until the correct offset is reached, thereby
allowing their developers to assume a monotonic system clock.

Nick




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