Tavern Ruffian

Before a player untaps their permanents during the untap step, the game checks to see if the day/night designation should change.

If it is night, and the active player of the previous turn cast two or more spells during their turn, it becomes day.

If you cast a spell with daybound during night, that spell will be front face up (that is, daybound face up) on the stack. However, it will enter the battlefield with its back face up (that is, with its nightbound face up). It won't enter with its daybound face up and then transform.