Can people say unequivocally that Jesus' resurrection was Sunday morning and not late Saturday night?
It is not even universally agreed which day Jesus was crucified
Short version : yes as SDA we believe Jesus resurrected on Sunday morning.
(I can dig on the day of crucifixion if you will, you can just ask
)
Longer version :
The earthquake and the rolling of the stone closing the tomb happened clearly on Sunday morning, a little bit before dawn.
Mat 28:1-2 KJV 1 In the end of the sabbath, as it began to
dawn toward the first day of the week, came Mary Magdalene and the other Mary to see the sepulchre. 2 And, behold, there was a great
earthquake: for the angel of the Lord descended from heaven, and came and
rolled back the stone from the door, and sat upon it.
Not only that, but Jesus did not ascend to heaven to see his father before later that morning. Indeed, he met Mary and told her :
Jea 20:17
Touch me not; for I am not yet ascended to my Father: but go to my brethren, and say unto them, I ascend unto my Father, and your Father; and to my God, and your God.
So, from the Bible, it would be pretty far fetched to assume Jesus was resurrected many hours before all that. On the contrary, the most reasonable (and accepted) understanding is Jesus resurrection on Sunday morning.
Now I agree that I don't know of any text that say specifically and literally that he resurrected on Sunday morning, but because of the many indirect evidence we have of that, I don't think any other hypothesis would be Bible based.