In z/OS > 1.8 you can use the MVS SET TIMEZONE command to set a new time for displaying entries (internal date is unchanged) and doesn't need an IPL.
We can use that for the daysaving hour change.
The first is change the SYS1.PARMLIB.CLOCKXX TIMEZONE value.
OPERATOR NOPROMPT
TIMEZONE W.12.00.00
ETRMODE YES
ETRZONE YES
STPMODE YES
STPZONE YES
TIMEDELTA 10
TIMEZONE W.XX -> From Greenwich to WEST
TIMEZONE E.XX -> From Greenwich to EAST
Take that on mind if the change is +1 or -1 hour.
The next one is apply the new setting in the working system.
To do that set the same timezone with this MVS command:
T TIMEZONE=W.12
Later, we must made the change on OMVS: Edit /etc/profile and /etc/init.options files and set TZ=CST13PDT (for example)