This is a ridiculous argument. The calendar has had so many adjustments, that the Sabbath may be any day of the week. Will observing the Sabbath on the wrong day prevent us from entering the Kingdom of God. No! Only the denial of Christ as you Savior will. I pray that no one will deny Him.
Christians all agree that the Sabbath is on Saturday. It is a day of rest, that is poorly observed by both Christians and Jews. (again, study the Law as it relates to what man can do on the Sabbath) Now the difference. We also celebrate the resurrection of our Lord and Savior on Sunday. This is not an observance of the Sabbath. It is the day that we take to prepare for the next week.
I am sorry friend but this is simply not true. I refer to your point:
"This is a ridiculous argument. The calendar has had so many adjustments, that the Sabbath may be any day of the week."
By this I know you have not even tried to see if we do know the day or not. We do know the day very clearly. if you had studied into this you would know that while the calendar has changed the days of the week never have. while the 2nd day has always been followed by the 3rd. but the date changed. so the 2nd may have been the 12th of march and then the 3rd became the 18th of march. my point is that the days of the week have not changed just the date applied to them.
The day has even changed name but the cycle has remained the same. If you really want to know which day is the 7th you need only go to the Jewish nation. They have a history which is recorded in the bible. God told them in exodus 16 to obey the Sabbath.
Does God know which day it was? Yes.
The Jewish nation followed that because it was in grained in them for 40 years in the desert by the falling of manna.
The bible also tells us which day it is,
Luk 23:54 And that day was the preparation, and the sabbath drew on.
Luk 23:55 And the women also, which came with him from Galilee, followed after, and beheld the sepulchre, and how his body was laid.
Luk 23:56 And they returned, and prepared spices and ointments; and rested the sabbath day according to the commandment.
Luk 24:1 Now upon the first day of the week, very early in the morning, they came unto the sepulchre, bringing the spices which they had prepared, and certain others with them.
Luk 24:2 And they found the stone rolled away from the sepulchre.
Luke tells us what Day the Sabbath is everyone knows that Jesus rose on the Sunday. this is where Christians get their tradition of Sunday Sabbath from. Funny how many claim the knowledge of the day He rose but seem ignorant of the day he rested just before. which like says was the Sabbath according to the commandment.
Now lets apply a little logic, what day comes before Sunday?
Answer: what we call Saturday. see it was not that hard.
You know this as your post suggests in the second paragraph so why does your first paragraph say what it does. we do know very clearly which day is the 7th.
It is poorly observed but not by all. most do however not observe it at all. By the law is the knowledge of sin. so that fact that you know this does not bode well for you now does it.