Time not according to timezone

I run HA OS (latest) on RPI.
Lately my homecountry Germany switched from CET to CEST (Central European Summer Time), so +1 hr. Although I get correct CEST output when I enter “date” in SSH, my heating timetable (the valve is a Zigbee device, run by Zigbee2MQTT) does not match CEST anymore. It´s one hour behind now and seems to be stuck in CET.
Our Internet Router ist configured to a local NTP and getting the correct CEST also.
How can that be?