They moved the BoB cocktail party because the weather was unpredictable. A different commemoration that I attend moved from the 3 week in October, the night of the action, to the first weekend for the same reason.
As the dwindling number of survivors are growing ever older the date has now been moved forward another week in to September.
At least they have a good reason as it is a small commemoration and age is wearying them. Not so now the annual BoB cocktail party that ought to be returned to its rightful date.