F-ckin Leap Seconds, how do they work?

Owen DeLong owen at delong.com
Tue Jul 3 23:53:32 UTC 2012

On Jul 3, 2012, at 1:09 PM, Saku Ytti wrote:

> On (2012-07-03 12:46 -0700), Owen DeLong wrote:
>> If you don't know that time is not monotonically increasing, then that only becomes a software bug when you codify your own ignorance into software you write.
> If only all software could be ordered from you Owen, but in practice this
> is not possible. Some code will be written less intelligent people. And
> reviewing any code doing foo = timestamp+offset and if now > foo, virtually
> never expects time to move backwards.

Sure, but even with that, 99% of it has only a passing 'interesting' effect and
then recovers.

> UTC doesn't move backwards (it goes 59 -> 60 -> 00). TAI does not move
> backwards. Unixtime moves backwards, like spanish inquisition no one
> expects that.

UTC (and the system clock) should not move backwards, but, rather they repeat
second 59. UTC goes 58->59->00 most of the time, but during a leap second, it
should go 58->59->59->00). It's not so much going backwards as dropping a chime.

>> It is well known that leap seconds exist.
> Quite. But it is not well known that unixtime travels backwards.

In part because it shouldn't actually do so. It should simply chime 59 twice.


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