GGB Work it backwards rather than picking a start date. Fix opening night, then walk each role back through its full chain — search, offer, notice period, work authorisation, relocation, induction and training to demonstrated competence. Leadership goes first because its chain is the longest and every later hire depends on it. The practical trigger: the moment your opening date is credible and funded, the manpower plan should exist and the leadership search should already be moving.
From The Pre-Opening Recruitment Calendar — Hiring Backwards from Opening Night — the full reading, with the method behind this answer.