I created an event with an alarm im my home timezone (UTC+1). Now I am travelling. I temporarily set my timezone to a new value (UTC-8). The alarm goes off at the right time according to my home timezone, but I cannot dismiss the reminder. The reminder window keeps popping up when I click “Dismiss”.
So, in the meantime I noticed a pattern… I can dismiss an alarm that went off according to my home timezone when the same time is reached in the new timezone. For example, given the timezones I mentioned above, I can dismiss an alarm 9 hours after it went off.