Which day is the true biblical Sabbath on?

It has come to my mind after having a debate with a Christian that the Sabbath is a major obstacle to the true worship of God. The Christians claim that Jesus changed the Sabbath to Sunday because he rose on a Sunday, but then again the Jews keep the seventh day Sabbath on Saturday and also claim rightfully that Jesus was a Jew. I would like opinions based on facts please. My personal view is you cant change the last day of the week to the first, so the Jews are right.