lol!
reason is simple. putting a fixed date, if they can't deliver due to unforeseen circumstances, they will have to answer to a lot of queries.
it is just a way to cover backside. if can deliver earlier than deliver lor... if cannot, no choice, still got the last day to fall back on.
Generally, there will be about 500 happy people and probably 2,600++ people feeling emo over the long weekend.