Please provide full, real world examples with *actual* data. And 
please answer *all* questions.

These are calendar events. created with the "New Event" button (+ 
button) in the Kronolith "month view"

If the date.timezone is set in php.ini, and an event previously 
created for 3pm, for example, with the "Alarm 1 hour before event 
starts" option, the alarm will be sent out at the event time, not an 
hour before, if the alarm was set when Daylight savings time *IS* in 
effect, for a time when DST it is *NOT* in iffect.

Removing the php.ini  date.timezone entry makes Kronolith work as expected.

The correct timezone was set in php.ini, and everything else works 
properly including times in other horde apps, only the alarms are off 
by an hour.

Please provide a more detailed bug report. Which settings work, which 
don't. How did the event look like, how did you trigger alerts, when 
did you trigger alerts, what was the exact outcome, etc.

If the date.timezone is set in php.ini,  the alarm will be sent out an 
hour late when Daylight Savings Time expires.

Workaround:
Commenting out the date.timezone entry seems to fix this, however 
doing so may break other applications that expect it to be there.