There is no eighth day of creation. God has never taken up the work of creation again, and that’s why a word that also means ceased was used in describing His Sabbath rest.
“Just as Jonah was three days and three nights in the belly of a huge fish,” He said, “So will the Son of Man be three days and three nights in the heart of the earth (Matt. 12:40).”
Over the next 40 days before His ascension, Jesus appeared to more than 500 people, and later came back to personally prepare Paul to carry His message to the Gentiles.
The special Sabbath John referred to is the Feast of Unleavened Bread, and it’s a date specific holy day; always observed on the 15th of the month they call Nisan, which corresponds to March/April on our calendar.