Matthew 12:40 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.
These are the words Jesus spoke. If He said three days and three nights I will believe His math. Sunset to sunset makes a day in the Hebrew numbering of days and nights. There is no 24 hour period.
Sunset to sunset is 24 hours.
Thursday night could “technically” be included in the day Friday, but he wasn’t “in” Heart of the earth until Friday at 3:00.
And Jesus said to him, “Assuredly, I say to you, today you will be with Me in Paradise.”...
Then he took it down, wrapped it in linen, and laid it in a tomb that was hewn out of the rock, where no one had ever lain before. That day was the Preparation, and the Sabbath drew near.
And the women who had come with Him from Galilee followed after, and they observed the tomb and how His body was laid. Then they returned and prepared spices and fragrant oils. And they rested on the Sabbath according to the commandment.
Now on the first day of the week, very early in the morning, they, and certain other women with them, came to the tomb bringing the spices which they had prepared.
Luke 23:43,53-24:1
JLB