It depends on whether the world you are playing in is a one-game-per-day world or a two-game-per-day world. For the one-game-per-day worlds, all games (except exhibition games) are simulated between 2-4 am ET. Exhibition games are simulated between 2-4 pm ET. For 2 games per day worlds, games are played both in the afternoon and overnight, between 2-4 ET.