Somebody works it out on their fingers, usually around Easter, usually a teenager who has just noticed. Friday afternoon to Sunday at dawn is one night, one day, one more night. The answer is that he did not spend seventy-two hours in the tomb, and that the Gospels are not claiming he did.
I went looking for a problem here and did not find one. That happens less often than it should, so I want to say it plainly before going any further: the ordinary answer holds.
Counting it on your fingers
For as Jonas was three days and three nights in the whale’s belly; so shall the Son of man be three days and three nights in the heart of the earth.
Matthew 12:40 (KJV)
Three days and three nights, twice in one sentence. Set that beside Mark, who says the burial happened on the preparation, the day before the sabbath, and then has the women arriving at the tomb very early on the first day of the week. Friday evening, sabbath, Sunday sunrise. Two nights, not three.
The objection is a fair one.
Scripture counts days out loud
What settles it is not a rabbinic footnote. Scripture uses both phrases for the same span, in the same passage, more than once.
And they gave him a piece of a cake of figs, and two clusters of raisins: and when he had eaten, his spirit came again to him: for he had eaten no bread, nor drunk any water, three days and three nights. And David said unto him, To whom belongest thou? and whence art thou? And he said, I am a young man of Egypt, servant to an Amalekite; and my master left me, because three days agone I fell sick.
1 Samuel 30:12-13 (KJV)
The same man, in consecutive verses, has gone without food three days and three nights and fell sick three days ago, which is one period given two phrasings by one writer who saw no difficulty in either.
Esther tells the Jews in Shushan to fast three days, night or day, and then goes in to the king on the third day. On a stopwatch she walks in early, on the third day of a fast with a day still to run. Nobody reads the chapter that way. Joseph puts his brothers in custody three days and speaks to them on the third day. And Rehoboam tells Israel to come back after three days, in 2 Chronicles 10:5, while verse twelve reports them arriving on the third day, as the king bade, saying, come again to me on the third day. One appointment and one king, given both phrasings seven verses apart.
The idiom is not being smuggled in from outside the book. The book uses it about itself, in narrative, where nobody is arguing about doctrine and nobody has anything to gain.
The Gospels give one sentence both ways
Jesus is quoted both ways in the same scene. Straight after Peter’s confession, Mark has Jesus say he will be killed and after three days rise again. Matthew and Luke record that same prediction, and both of them write the third day instead.
The copyists went further than that. Somewhere in the transmission one phrase became the other, twice, and Mark is where it shows: his other two predictions read after three days in the critical Greek text and the third day in the tradition behind the King James.
The chief priests use both phrases in one breath
The men who arrested Jesus did the same thing, and they had every reason to be exact.
Saying, Sir, we remember that that deceiver said, while he was yet alive, After three days I will rise again.
Matthew 27:63 (KJV)
They quote him as saying after three days. Then, in verse sixty-four, they ask Pilate to make the tomb secure until the third day. If after three days meant seventy-two hours, the guard they are requesting would come off before the deadline they are worried about, and Pilate would have noticed.
The disciples do the same thing walking to Emmaus.
But we trusted that it had been he which should have redeemed Israel: and beside all this, to day is the third day since these things were done.
Luke 24:21 (KJV)
Today is the third day since. Said on a Sunday, counting a Friday that had already ended as day one, by a man with no theological point to make and no reason to fudge it. He was disappointed, and disappointed men do not usually massage the calendar in favor of the story that has just let them down.
The serious version of the objection
There is a serious version of this argument. John records that the sabbath that week was a high day, which means a festival sabbath rather than only the weekly one, and some readers take that to mean two sabbaths fell in that week and the crucifixion was on a Wednesday or a Thursday, which yields a full seventy-two hours.
It takes Matthew 12:40 at maximum strength and it has a real textual hook. What it costs is Luke 24:21, where Sunday is the third day since, which works from a Friday and does not work from a Wednesday.
I think the inclusive reckoning is right, and I hold it knowing that careful readers have looked at the same verses and gone the other way.
Jonah was not a stopwatch
Jonah is not in that sentence as a stopwatch. Scribes and Pharisees had asked to see a sign, and the answer was that an evil and adulterous generation seeks after a sign and would be given one only, the sign of the prophet Jonah. He was refusing a demonstration and promising a death, and the measurement was never the point of either. A man swallowed, given up for dead, and returned.
The counting question is worth asking, and a teenager should ask it every Easter, because a faith nobody checks is a faith nobody is holding. In this case the checking lands where the church has always said it does. Not every popular reading is a misreading, and the tidy correction is not automatically the true one. Sometimes it is, as with a trade Mary Magdalene never had or the gate a camel was supposed to kneel through, and sometimes the thing everybody says is simply what the text says.
The women went at sunrise expecting to finish a burial. They found the reason anybody counts the days at all.