They do.
Note.—“You may read the Bible from Genesis to Revelation, and you will not find a single line authorizing the sanctification of Sunday. The Scriptures enforce the religious observance of Saturday, a day which we never sanctify.”—Cardinal Gibbons, in “The Faith of Our Fathers,” edition 1892, page 111.
“Sunday is a Catholic institution, and its claims to observance can be defended only on Catholic principles.... From beginning to end of Scripture there is not a single passage that warrants the transfer of weekly public worship from the last day of the week to the first.”—Catholic Press (Sydney, Australia), Aug. 25, 1900.
13. Do Protestant writers acknowledge the same?
They do.
Note.—“Is there no express commandment for observing the first day of the week as Sabbath, instead of the seventh day?—None whatever. Neither Christ, nor His apostles, nor the first Christians celebrated the first day of the week instead of the seventh as the Sabbath.”—New York Weekly Tribune, May 24, 1900.
“The Scriptures nowhere call the first day of the week the Sabbath.... There is no Scriptural authority for so doing, nor of course any Scriptural obligation.”—The Watchman (Baptist).
“The observance of the first instead of the seventh day rests on the testimony of the church, and the church alone.”—Hobart Church News (Episcopalian), July 2, 1894.
For additional testimonies, see reading on page [454].
14. How did this change in observance of days come about, suddenly or gradually?