I would just like to add that I am also having this issue. I will just leave my HTPC clock 1 hour incorrect as a fix for summer if it's not solvable for now.
I have the problem too. I am using xmltv plugin and have 2 hours of compensation during summer. Last week I lost all recordings after the change from summer- to winter-time. All recordings were 1 hour off. I had to manually modify from 2 hours to 1 hour offset in the xmltv-plugin. Developers - could you please add a checkbox in the xmltv plugin thats says "Compensate for daylight saving time"? Thanks in advance.
Note: The computer clock was changed automatically. The problem lies in the xmltv plugin offset functionality.