From Sabbath to Sunday is a translation and an adaptation of my Italian doctoral dissertation, originally presented at and published by the Pontifical Gregorian University in 1977. The investigation establishes that the change from Saturday to Sunday began approximately one century after the death of Christ, as a result of an interplay of political, social, pagan and Christian factors. The change in the day of rest and worship was not merely a change of names or of numbers, but rather a change of meaning, authority and experience. Essentially it was a change from a Holy Day into a holiday. From Sabbath to Sunday has the distinction of being the first book written by a non-Catholic ever to be published by a Pontifical press with the Catholic imprimatur (approval). The book has already been reprinted fourteen times in English and has been translated in several other languages. Hundreds of scholars of different persuasions have praised this book as a definitive treatment of the early history of the Lords Day. I received a gold medal from Pope Paul VI for earning the academic distinction of summa cum laude in my research and school work at the Pontifical Gregorian University, in Rome, Italy.