If you've read the account of Jesus crucifixion in the Bible, you know it was a bad day.
Matthew 27:28-30 -- They stripped him and put a scarlet robe on him, and then twisted together a crown of thorns and set it on his head. They put a staff in his right hand and knelt in front of him and mocked him. "Hail, king of the Jews!" they said. They spit on him, and took the staff and struck him on the head again and again."Struck him on the head again and again." With a staff (that is a stick, pole or rod). Again and again. Good Friday?
They mocked him and forced him to carry his own cross. He was hung there. He experienced great pain, and he eventually died there. Good Friday?
He was put into a tomb.
However, soon came Sunday, and a great and marvelous thing happened. Jesus rose from the dead! Because of this we may have eternal life if we believe. See the cost (wages) of sin is death, eternity away from God. But Jesus lived a sin-free life. He didn't deserve death. But on that terrible Friday he died, paying the price for our sins. And when he rose again, he opened the doors to heaven so that all us sinners could have not death, but eternal life.
That was a very Good Sunday. Resurrection Sunday. Easter Sunday. That Friday was an important day, the day our Savior died for us. But to me, the GOOD day, the great day was Sunday.
John 11:25 -- Jesus said to her, "I am the resurrection and the life. He who believes in me will live, even though he dies."