Normally if changing the time only during Daylight Saving time changes there is no need to recycle the CV since IDMS 18.5, see TEC1158388.
However, if changing the system date to a past date you need to recycle the IDMS CV and reformat the IDMS log and journal files.
Firstly you need to make sure there is a normal IDMS CV shutdown (i.e. no abend).
The journal and log records store the date so to avoid duplicates you will need to archive the journal and log files and them re-format them.
See QI52458, it is similar to the "PROCEDURE FOR EXITING DAYLIGHT SAVING TIME BACK TO STANDARD TIME"