The Biblical day begins in the evening (Gen 1:5,8,13). On that occasion the disciples had met on Saturday evening, not Sunday.

The terminology “to break bread,” when used in isolation, does not necessarily refer to Holy Communion, which always includes “the cup of blessing” (1 Cor 10:16; 11:23-29; Mt 26:26-29). Breaking of bread can refer to a daily meal or fellowship meal (Acts 2:46; 27:35-36). Acts 20:7-8 describes a farewell meal for Paul who was walking to Assos the next day (Acts 20:13-14). There was no Sunday service at all.