There's a valid alternative explanation that reconciles what Jesus said about how long he would be in the grave:
Mat 12:39 But He answered and said to them, "An evil and adulterous generation seeks after a sign, and no sign will be given to it except the sign of the prophet Jonah.
Mat 12:40 For as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth.
Jesus said "three days and three nights." And he used the timespan of Jonah in the fish to compare.
Now ask this question: How long did the people Christ was talking to think that Jonah was in the fish? Why would Christ say "three days AND three nights" unless they knew exactly how long Jonah was in the fish. They knew how long because scripture told them:
Jon 1:17 Now the LORD had prepared a great fish to swallow Jonah. And Jonah was in the belly of the fish three days and three nights.
So three days AND three nights. Most who believe in a Friday death and Sunday resurrection will say that this is a "Jewish" saying that could mean any part of a day or night. Yet even using this there is no way to get three days and three nights. And if that were true then there would have been uncertainty about how long Jonah was in the fish. So when Jesus said like Jonah, three days and three nights, if they weren't certain of the exact number of days and nights they would have said "What do you mean? Nobody really knows how long Jonah was in the grave. Three days and three nights is just a jewish saying."
But what if it literally WAS three days and three nights? Three full days and three full nights? There is a way to make this work which involves the first day of unleavened bread (or what modern jews call the start of passover) starting on Wednesday night the year of the death of Christ.
Where do you find this in scripture?