On Fri, 24 Oct 2025 16:01:50 -0500, Paul Gilmartin <[email protected]> wrote:

>This problem was solved long ago: <https://www.iana.org/time-zones>
>Inexplicably, IBM shuns that solution, almost pervasive elsewhere.  NIH?

IANA solution does not solve the time change problem (DST nor ST). 

Unix & Windows completely ignore the implications of that hour change. These 
machines are so much slower where an hour time change goes unnoticed. A single 
z/OS is many times more active and SYSPLEX makes this far more complex. 

>>that issuing the TIMEZONE W.05.00.00  or set CLOCK=hh.mm.ss commands should 
>>do the trick.

Time change occurs on Sunday's at 2:00am which will go unnoticed but there are 
still risks.  

Some STC's have an optional timezone specifications that can override the z/OS 
timezone (e.g. CICS) for the product. If you never use them, then they most 
likely won't be a problem.

Do you avoid specifically specifying Sunday between 1AM to 2AM (e.g. 
automation, job scheduler and more). For instance, does a job scheduled for 
1:30am run twice for DST and never run for ST. I would hope job schedulers warn 
you but some products might not.

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