Continuing Ingolf's tradition this post is about z/VSE considerations for the upcoming Dayling Saving Time (DST) change in October/November 2020 to local standard time. The clock is turned one hour backward on:

• USA: Sunday, November 1, 2020 at 2 a.m. local daylight time
• Germany: Sunday, October 25, 2020 at 3 a.m. local daylight time

Regarding z/VSE considerations I'll quote Ingolf from his post from February 2, 2019 in Ingolf's z/VSE Blog:

"A local time change forward has normally no effect on subsystem operation. It may have an impact on accounting, however. A local time change backwards could affect subsystems and accounting routines more severely. Therefore I recommend to IPL the z/VSE system for any time changes.

With the z/VSE IPL commands SET ZONEDEF and SET ZONEBDY you can switch between standard and daylight local times without changing the IPL startup procedure each time. However, you have to IPL the system in order to switch to the new time zone. See the z/VSE System Control Statements manual for details."

References:

• z/VSE System Control Statements, section SET ZONEDEF / SET ZONEBDY
• z/VSE Administration manual, section ZONE Specifications and Daylight Saving Time, subsections ZONEDEF Specification and ZONEBDY Specification
• IBM Support document Daylight Saving Time changes effect on CICS TS
• z/VSE Hints and Tips, section System Date and Time
• Technical article z/VSE and Changes to Daylight Saving Time (DST)

I greatly appreciate your feedback either in the comments or via the z/VSE contact form.

Disclaimer: My posts and opinions are my own.