Just need 12 more likes in Fan Page fb. If fb hit 1k likes whether HH will be start at the time when fb got 1000 likes or what?
Admin will announce that schedule of the Happy Hour if the Facebook page reaches 1k.
Hope this answers your question.

Yup, it makes sense for everybody to be aware that it is Happy Hour.
We had a hidden happy hour last time around. Won't be repeated again.