The date was March 31, 31 AD when He resurrected. That was 3 days and 3 nights after He was crucified March 28, daytime Wednesday."sabbatou" is not intended for "week" in Scriptures. Jesus resurrected πρωῒ πρώτῃ σαββάτου = early morning of the chief sabbath. That's Saturday.
But why AD 31, instead of 30 AD?
John recorded 3 passover feasts that transpired AFTER the baptism of Jesus. The last passover was on His crucifixion. He was baptized in the 15th year of the imperial reign of Tiberius whose first year of reign as emperor was in 14 AD. He was therefore baptized in 28 AD, and the first Passover was in 29 AD; the 2nd in 30 AD and the last was in 31 AD, when He was crucified.
But why March 28 in 31 AD?