The question is not about the definition of holy.
The question is about what Scripture means.
In Rom 12:1 Paul beseeches us: I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service.
I asked you what this meant.
Specifically, on what day or days this Scripture did not hold.
The only answer that could possibly apply is that this command or exhortation is true for every day of the week.
There are no exceptions.
Also, it may surprise you to know that, almost without exception, the word "holy" in the New Testament is used to qualify people.
Not days and not objects.
Rom 12:1 is an excellent summary of worship before God.
It is not valid on some days and invalid on others.
Now for some bigger picture things:
The Law in any way, shape, or form is not the final arbitrator that defines the behaviour of Christians.
The Law , in the nature of the Law, can only inform us of our transgressions.
It can only function as a minimum standard of what a transgression is.
Jesus Himself points this out in the Sermon on the Mount where he uses the examples of murder and lust to point out the real meaning of what these things mean. Up to that point everyone interpreted the Law to mean murder = killing someone; and adultery = sleeping with someone of the opposite sex when married. Jesus rapidly sets out the real meaning of those commandments for His audience.
The problem is that the Law cannot deal with the thoughts of the mind. How can the Law know whether I wish someone dead or lust after some woman.
Paul call the Law a tutor - it teaches us, to a degree what sin is. But as comprehensive as it is, it cannot convict anyone, on earth, based on our thoughts.
Paul also makes it absolutely and unequivocally clear that the Law, and observance of the Law cannot save.
All it can do is convict.
The Law, including the commandments given to Moses, are just weak types of what, as believers in Christ, we are called to.
Believers in Christ are not called to minimum observance of any code of law.
Instead we are called to maximum love of God.
With respect to the 4th commandment, in particular, we are not merely called to give one day per week to God but rather everything and everyday - just as is spelt out in Rom 12:1.