A drink poured at 01:30 belongs to the night that started the previous afternoon. Every hotel reporting standard treats it that way, and a system that files it under the new calendar day will disagree with its own bar takings every single night.
Vestibel stamps a business date on every payment, order and folio charge at the moment it is written, using a rollover time the property configures. Reports read that stamped column rather than re-deriving it, which is what makes a closed day immutable: changing the rollover time next year cannot retroactively rewrite last year.
The night audit itself closes the oldest day that has already ended, posts that night's room charges, and freezes a revenue snapshot. It never closes the day in progress, and an unreconciled cash drawer is the only thing that blocks it — guests owing money at 3am is the healthy steady state, not an exception.