hiya mate,...i think the fact you see it as an "event" is why your looking for a start and finish time,...
we dont do a roll call,...(Raikey?..here sir!!,...) hahaha
short answer, there are no start and finish times,...
the 19th is a Saturday,...just turn up when suits you,..7am, so you can get a good day in ..or 4 pm so you can get setup before the sun drops,....
then Sunday the 20th get up, have breakfast, and pack up,...or strike camp after lunch and hang around until it gets late,...
its a generally relaxed vibe with no real agenda or concrete itinary,..
i hope this helped,...
Cheers
Stu