My system got notifications about a new “next AlarmTime” although no alarm was set on any connected device. I started wondering where the h… this was coming from.
A deeper look brought up that an actually used timer is also considered as an alarm and send to my openHAB server.
Reading the docs I wouldn’t have understood it that way. Is this behaviour intended or just so because there is no way around it?
This. Whenever any app uses the AlarmManager api of Android, it’s recognized by openHAB as next alarm time.
However some apps are on a ignore list, so they never cause any alarm time updates at openHAB: openhab-android/mobile/src/main/java/org/openhab/habdroid/background/BackgroundTasksManager.kt at main · openhab/openhab-android · GitHub
Does the app you use as timer also offer an alarm clock?
Thanks for the reply, the answer was expected.
I am ( or better we are) using the standard clock app of our android devices for mainly for the wakeup time. My use-case is to check whether hot water is provided at wakeup time, if not it will be switched on.
What I did not foresee was the use of the timer ( mainly by my wife). 
I guess we have to live with that or disable the rule.
Maybe you could add a check to the rule whether the alarm time is in a range of typical wake up times for you, e.g. 6:00 - 8:00.
Thanks for this one.