New Orleans, Detroit, and Orlando all have rock concerts scheduled for Saturday night, so no day or night game on Saturday in those arenas. Los Angeles has an arena football game on Saturday evening, and Boston has a possible day or night hockey game, so there is a possibility of a basketball game in the afternoon at the Staples Center, or a day or night game at the Garden. It's possible to have two sports events on the same day, but a rock concert needs the arena for the whole day and evening.
Utah, Cleveland, and San Antonio do not have events scheduled for Saturday, and none of the eight arenas has anything booked for Sunday.
More information, but it still doesn't tell us for sure when the Celtics will play! We'll know by tomorrow morning.