The event starts at 12 mid day day finishes at 21:00 as Mark stated. I'm not sure what time they will open the gates though so best check on their site to be sure
I just phoned Santa pod. The gates open a 8am, and they reckon the track will be open at 9am. Drag events go on til 9pm, but towards the end is the jet car and entertainment so prob aroun 8pm we'll have to stop.