I don't think your link properly explains why the Sabbath was changed. How about a look at historical evidences;
"Unquestionably the first law, either ecclesiastical or civil, by which the sabbatical observance of Sunday is known to have been ordained is the sabbatical edict of Constantine, A.D. 32I."
Chambers' Encyclopaedia, Article "Sunday."
"On the Venerable Day of the Sun ["venerabili die Solis"--the sacred day of the Sun] let the magistrates and people residing in cities rest, and let all workshops be closed. In the country, however, persons engaged in agriculture may freely and lawfully continue their pursuits; because it often happens that another day is not so suitable for grain-sowing or for vine-planting; lest by neglecting the proper moment for such operations the bounty of heaven should be lost--Given the 7th day of March, [A.D. 321], Crispus and Constantine being consuls each of them for the second time."
The First Sunday Law of Constantine 1, in "Codex Justinianus," lib. 3, tit. 12, 3; trans. in Phillip Schaff "History of the Christian Church," Vol. 3, p. 380.
"The Council of Laodicea - forbids Christians from judaizing and resting on the Sabbath day, preferring the Lord's day, and so far as possible resting as Christians."
Encyclopaedia Britannica, 1899 Edition, Vol. XXIII, page 654.
"Christians shall not Judaize and be idle on Saturday [in the original: "sabbato" shall not be idle on the Sabbath], but shall work on that day; but the Lord's day they shall especially honour, and as being Christians, shall, if possible, do no work on that day. If, however, they are found Judaizing, they shall be shut out from Christ."
Council of Laodicea, c. A.D. 337, Canon 29, quoted in C.J. Hefele, "A History of the Councils of the Church," Vol. 2, p. 316.
It would appear that the Sabbath was changed by a commandment of men. What do you suppose Christ thinks about men changing his Fathers commandments?;
Mat 15:1 Then came to Jesus scribes and Pharisees, which were of Jerusalem, saying, 2 Why do your disciples transgress the tradition of the elders? for they do not wash their hands when they eat bread. 3 But he answered and said to them, Why do you also transgress the commandment of God by your tradition? 4 For God commanded, saying, Honor your father and mother: and, He who curses father or mother, let him die the death. 5 But you say, Whoever shall say to his father or his mother, It is a gift, by whatever you might be profited by me; 6 And does not honor his father or his mother, he shall be free. Thus you have made the commandment of God of no effect by your tradition. 7 You hypocrites, well did Isaiah prophesy of you, saying, 8 This people draws near to me with their mouth, and honors me with their lips; but their heart is far from me. 9 But in vain they do worship me, teaching for doctrines the commandments of men.