Need to store dates in an explicit intentional form (e.g. 2008-12-23-12-34 rather than as an absolute value (e.g. 12363626367) calculated at the time of entry. This would solve the problems of dates altering when governments change the time with "daylight saving" etc. Moodle would just look up the intentional date and apply that to whatever the current time/ date setting was at the time.
The problem is created by the calcuation of an absolute time in the future when the event is entered.
Making moodle process intentional times from the database rather than absolute times would involve a bit more processing, but woul dsolve all these issues without needing to invent a huge number pof rules for daylight saving.