Acts 20:7 “And on the first day of the week, when we were assembled
to break bread, Paul spoke with them because the next day he was
ready to depart, And he continued to speak until the middle of the
night.”

In fact this meeting cannot refer to a Sunday morning “church service”
because it says “he continued to speak until the middle of the night”
(20:7). Certainly we are not to believe that Paul was so long winded
as to have spoken for well over twelve hours! Clearly this was an
evening meeting. This is also evidence in the next verse which states
“there were many lamps burning in the upper room in which they were assembled” (20:8). Jewish days run from evening to evening (Gen. 1:5-31; Lev. 23:27, 32). (Thus the Sabbth runs from sundown Friday until sundown Saturdy). An evening meeting on the “first day of the week” by Jewish reckoning would be what we call Saturday night. In fact Jews have always and still do gather on Saturday night for a service called Havdalah. Havdalah is a service held to mark the end of the Sabbath and initiate the beginning of the week.

Paul had been resting on the Sabbath and was prepared to leave at
daybreak (i.e. “the next day”). This usage of the phrase “the next day”
or “tomorrow” to refer to daybreak rather than the next calendar day is common in ancient Jewish usage (Gen. 19:34 for example).