The Sabbath, part 2: from Saturday to Sunday

"I used to think people who kept the Sabbath were ignorant and legalistic. Hadn't they read Colossians 2 and Romans 14? Didn't they know the Sabbath is on the Saturday and not the Sunday? But I had been reading biographies and I had made a troubling discovery. All the great missionaries, evangelists, preachers, hymn-writers kept the Sabbath and they did so on the Sunday." Here's why for centuries Christians observed the Sabbath on the Sunday and why it should be observed on Sunday still in our day.