One feature is that some sites use different times in different regions. I. E. a Japanese, Indian, European, Eastern US, Western US time zones. All implemented with different offsets from UTC. And IBM spreads leap seconds over the affected minute.
On Tue, Oct 28, 2025 at 3:15 PM Paul Gilmartin < [email protected]> wrote: > On Tue, 28 Oct 2025 14:41:57 -0500, Jon Perryman wrote: > > > >Even in the Unix world this is not always true. For instance, repeating > events in a calendar where global participants are not sharing the event > and have their own unique event. You don't get a warning about time changes > > > True. It would be better to share the event. > > >For z/OS system products, IANA is irrelevant. z/OS, CICS and ??? allow > for 1 local timezone and planning for time change may be needed. Certainly > the impact is far less at 2:00am Sunday than during the 2:00pm on Thursday > but the possibility exists. > > > There are more than two timezones that z/OS supports/ > > >> Nothing changes, neither system control blocks nor code. > >> at 02:00 on that Sunday morning. > > > >Clearly you don't understand the complexity of time change and the > system. For instance, job abc must start at 2:00am to guarantee is > completes by 6:00am. Does the job scheduler start it at 1:00am or do you > accept that the job completes after 6:00am. > > > Enter 6:00am in struct tm; call mktime; subtract 4*60*60 seconds; call > localtime. > But this is best done in UTC because 0200 occurs twice next month. > > >Just because you don't understand the problem doesn't mean the problem > does not exist. > > > The problem exists; z/OS deals poorly with it. > > >>a system clock value and a timezone yields identical result for > identical input regardless > >>when it is called. > > > >Sunday 4:00am minus 1:00am can be 2, 3 or 4 hours if using local time to > calculate. > > > This is best done using UTC, not local. > > >>z/OS should awaken to this fact, well known everywhere else in the IT > world, > > > >ROTFLOL, the rest of the world has a single environment (processes and > threads). z/OS does not have a single environment (CICS, IMS, TSO, batch > and more). Implementing localtime in z/OS has never been a priority. > Customers needing this have written their own implementation. Simply put, > local time is not a priority because customers can easily implement their > own solutions which could include IANA. > > > ??? z/OS can be excused for doing it poorly because users could do > it better with considerable redundant effort. > > -- > gil > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
