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.

What was predicted of Christ's preaching?
In what two great commandments is the law of God briefly summarized?
With whose blood was the new covenant dedicated?
On which day was a double portion of manna gathered?
6. What influence do the Bible and history show working in the church immediately after apostolic days?
What fate awaits those who turn a deaf ear to the poor?
Who will walk in the light of the city?

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