You said this a month ago to David Jay, "But was it common for Semitic dialogue to say that a daytime or a night time would be involved with an event when no part of the daytime or no part of the night time could occur?"
My comment is a reply to clarify to you that the days and nights did occur. The reasoning behind the accepted missing night revolves around the biblical text that says the body could not be removed on the sabbath. (John 19:31) If you incorrectly assume that the sabbath being spoken of is the weekly sabbath (friday evening to saturday evening) then friday night + saturday night is only 2 nights.
If the sabbath that begins the evening after passover is used for counting there is no missing night. It's as simple as counting back 3 nights from sunday morning and arriving at a sabbath. The first day (evening to evening) of the feast of unleavened bread is a sabbath.
My point is, contrary to your statement to David Jay, the saying doesn't HAVE to be a colloquialism/common expression...without basis in reality. 3 nights in the heart of the earth can be understood as 3 nights in the tomb based on reckoning the jewish calendar of events preceding the resurrection. By doing this the 3 nights "fit" between a sabbath and sunday morning.
Note: the day of preparation spoken of in john 19:31 would be the day that all traces of leaven are removed from the home in preparation for the 7 day feast of unleavened bread. The evening of that day starts the sabbath.