Some contend that while the Jewish Sabbath is the seventh day of the week, the Christian Sabbath is the first day, or Sunday. Others believe that the Sabbath is on the seventh day for everyone. To further complicate things, some claim that, biblically, days don’t begin in the evening but instead begin in the morning—thus, even the Sabbath should start on Saturday morning instead of Friday evening at sundown. What day is the Christian Sabbath? Do biblical days begin in the evening or the morning? And why does any of this matter?