On Tue, 14 Mar 2023 12:45:27 +0000, Peter Relson <[email protected]> wrote:

><snip>
>What I would especially like to be able to know under z/OS are the following 
>timer values:
>
>DST offset - The Daylight Savings Time (DST) offset relative to UTC in minutes.
>
>And what's missing - even from lsstp - is the date and time when switching 
>to/from DST, i.e., the timezone setting, in the STP server, if it's set up to 
>auto-change the clock in the spring and fall.
></snip>
>
>I'd say that z/OS has no concept of DST offset or switching to/from DST.  
>Changing to accommodate DST is left as an exercise for the customer.

But you can't perform that exercise in a meaningful way without the right data, 
and that data is not available directly to applications (e.g. via PTFF).  It 
*is* available to the OS, however, who can make it available to apps.

If configured to do so, the z/VM Control Program obtains from STP the standard 
and DST time zones associated with the CTN at IPL.  It's up to the customer to 
actually change the TZ dynamically via CP SET TIMEZONE or to re-IPL, as they 
wish, but system automation *could* orchestrate either action.

A TZ change only affects CP and CMS.  No virtual TOD clocks are harmed, so 
non-CMS guests are unaffected. Sadly, we don't yet virtualize STP.  Maybe 
someday.

QUERY TIMEZONE                                                  
Zone  Direction   Offset   Status         Boundary          
UTC     ----      00.00.00  Inactive                         
GMT     ----      00.00.00  Inactive                         
EDT     West     04.00.00  Active-(STP)                     
EST     West     05.00.00  Inactive-(STP) 02:00:27 11/05/23 
Ready; T=0.01/0.01 11:14:34

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