Do Protestant writers acknowledge the same?

Answer

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, July 2, 1894.
For additional testimonies, see reading on page 146.

Of what is Christian baptism an evidence?
What did the prophet say His name should be called?
In what words does Christ recognize marriage as of God?
What will happen if a child is not properly instructed?
What special reason did the Israelites have for keeping the Sabbath?
From what time was Christ, the Word, associated with God, the Father?
What has been promised in order that man may be redeemed from this condition?

Questions & Answers are from the book Bible Readings for the Home Circle