CA Date Simulator should be stopped and re-started any time that the system clock is changed.
CA Date Simulator establishes a time adjustment factor based on the value of the system clock when Date Simulator was brought up and the user requested time/date value. If CA Date Simulator is executing when the system clock is updated for daylight savings time, it will be off by one hour until the next time that Date Simulator is restarted. If CA Date Simulator is executing when the system clock is updated for any other reason, it will be off by the amount of the change in the system time. If you routinely re-ipl your system at the daylight savings time transition, then Date Simulator will produce the expected results.
The discrepancy can be resolved by stopping CA Date Simulator and starting it back up.