On Mon, 26 Oct 2015 23:02:41 -0500, Joel C. Ewing wrote:
>
>Since UNIX and Windows platforms handle DST by just forcing the local
>time discontinuity, if an application has a problem with that, you don't
>have a choice other than tolerating the result or trying to find and fix
>any intolerable problems the discontinuity causes for the application.
>I'm sure there are cases on those platforms where a rare "strangeness"
>at time zone changes is just tolerated, since users in those environment
>traditionally seem to expect a higher level of s--- happens and some
>occasional apparent non-determinism..
> 
I'm trying to imagine my UNIX-oriented colleagues' snickering at the
idea of shutting down a system at the DST transition.  When they
stopped giggling, I'd expect them to ask, "But which time zone; which
country?  All?  Northern or Southern Hemisphere?  Both?"  UNIX
systems run their system clocks on UTC and an input to localtime()
is a time zone chosen by the programmer.  It would be absurd to
expect an hour's outage for each of several dozen time zones in
the world.  z/OS has a peculiar tunnel vision in its belief that there
are only two time zones.

Leap seconds are a different issue.  z/OS shuts down all applications
during a leap second.  Google and Amazon both steer their clocks
slow (less than 0.01 percent) for several hours centered on a leap
second.  And the two have chosen different steering durations.

-- gil

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