Was Jesus in the grave for exactly 3 days and 3 nights?
This is a very significant question to ask. It's one of the key proofs that Yahushua (popularly known as Jesus in modern English) is the true Messiah.
Yahushua Himself said so. Read Matthew 12:38-40:
Matt 12:38 Then some of the scribes and Pharisees answered, saying, “Teacher, we want to see a sign from You.”
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.
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.
The question now is: Did Yahushua fulfill this prophecy? Can this be proven from the scriptures?
As explained in the article “When was Jesus killed?”, He died in the mid-afternoon of Nissan 14 (or Abib 14 in Hebrew) which was the Passover day. In the Roman Calendar, this fell on April 5, 30 AD. It was also called the Preparation day.
Now, April 5, 30 AD was a Wednesday. He was immediately buried right before the sun had completely set in the ensuing evening. That evening was the start of the biblical 5th day (Thursday April 6, 30 AD in Roman calendar), which was the First Day of Unleavened Bread, an annual Sabbath.
Again, this is recorded in Luke 23:54 – 56:
Luke 23:54 That day was the Preparation, and the Sabbath drew near.
This is the annual Sabbath referred above, not the weekly 7th day Sabbath.
Luke 23:55 And the women who had come with Him from Galilee followed after, and they observed the tomb and how His body was laid.
56 Then they returned and prepared spices and fragrant oils. And they rested on the Sabbath according to the commandment.
After observing the First Day of Unleavened Bread on Thursday that week, the women returned and prepared spices and fragrant oils. Evidently, they did this on Friday because after doing all this work, they rested on the weekly 7th day Sabbath.
So far, how long had Yahushua been in the grave when the women rested at the start of the weekly 7th day Sabbath? He had been there since the Biblical Thursday started. This is the 1st night and the 1st day (evening to evening).
Biblical Friday would be the 2nd night and 2nd day. So far at this point, Yahushua had been in the grave for 2 complete days and nights.
What did the women do after the weekly Sabbath?
Matt 28:1 Now after the Sabbath, as the first of the weeks* began to dawn, Mary Magdalene and the other Mary came to see the tomb.
2 And behold, there was a great earthquake; for an angel of the Lord descended from heaven, and came and rolled back the stone from the door, and sat on it.
3 His countenance was like lightning, and his clothing as white as snow.
4 And the guards shook for fear of him, and became like dead men.
5 But the angel answered and said to the women, “Do not be afraid, for I know that you seek Jesus who was crucified.
6 “He is not here; for He is risen, as He said. Come, see the place where the Lord lay.
* Note: The original Greek for “weeks” in this verse is “sabbaton” σάββατον. This is the first of the 7 weeks pointing to the Feast of First Fruits, also called Feast of Weeks (See Lev. 23:15-17).
After the weekly Sabbath, when the women came to the tomb with spices and fragrant oils, Yahushua was already gone. He had risen evidently at the end of the Sabbath.
So the Biblical 7th day Sabbath would be the 3rd night and 3rd day Yahushua was in the grave.
Yahushua was definitely in the grave for a total of 3 nights and 3 days, or 72 hours. This fulfilled the prophecy He mentioned in Matthew 12:40.
Matt 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.
To recap, Yahushua was in the grave from end of Biblical 4th day Wednesday, when the sun has completely set at evening, through the end of the Biblical 7th day Saturday at evening, for a total of 3 nights and 3 days, as follows:
Biblical 5th day Thursday Nissan 15: 1 nighttime and 1 daytime
Biblical 6th day Friday Nissan 16: 1 nighttime and 1 daytime
Biblical 7th day Saturday Nissan 17: 1 nighttime and 1 daytime