Day // Night [TMID-19]

(If it becomes day or night or if a daybound permanent enters the battlefield, track day/night for the rest of the game.) As it becomes day, transform all nightbound permanents. If a player casts no spells during their own turn, it becomes night next turn. // As it becomes night, transform all daybound permanents. Permanents enter the battlefield nightbound. If a player casts at least two spells during their own turn, it becomes day next turn.