Holiday eve (trigger one day before)

I would like to do X (change lights) when its holiday eve (next day is the holiday),
I have the holidays calendar, my question is how can I do it the night before the holiday?


If you create the holiday events then HolidayName[-x,0] will start the event x minutes before the event start time in the calendar.

If you are using a calendar from someone else then setting gc_StartDelta to -x will start all events x minutes early