Not to butt in, but I'm butting in : )
**Bearing in mind that Judaism doesn't have it right either (their !!!Tradition!!! is a lot of what Christ was berating the Sadducees and Pharisees about):
The Torah says to REST on the Seventh Day. I am a Sabbath keeper, and that mainly means trying to devote Saturday to being with YHWH and removing myself from the cares of everyday life, with a distinct emphasis upon the Creation... And YHWH's REST. Judaism says no travel (walking is OK) - I adhere to that pretty much - and no work - which I adhere to with less emphasis - I try to prepare for the Sabbath by creating meals for Saturday before sundown on friday. I make no appointments on Saturday, and do no work, especially work for money. But while that is REALLY important, The ox does fall in the well from time to time. But for the most part, cold-cuts or cold leftovers as much as I can, or fasting sometimes... avoiding even doing dishes, laundry, and etc... spend the day in the Word, or studying topically, with lots of prayer time, quite often with a walk into His creation with the intention of being close to Him in the beauty of the natural world. Lots of ME! time with the Father, worshiping and music, but not to the exclusion of family (if I can help myself).
It has become a time I guard jealously, and look forward to.
All that in no way interferes with going to church on Sunday, to answer one of your questions: There is no day that is unfit for worshiping YHWH - But there is ONE DAY that He requires, and it is explicitly defined. It is the Sabbath Day.
To answer another question: I don't think that the apostles and the early Church had anything to do with moving the Sabbath. In fact, it is the Roman church who lays vigorous claim to that.
A Jewish friend of mine was able to shine a little light on the New Testament custom of worshiping on the 'first day of the week'... Because of strict prohibitions against walking too far, many people could not get to the temple or synagogue on the Sabbath, so it was already customary to have worship services after dark on Sabbath, which, being YHWH's time, after dark on the Sabbath is actually the first day of the week... It was his contention that the service where Paul talked deep into the night (and the kid fell asleep and fell out the window) was actually a Saturday night, and the service probably started at dusk on Saturday.
And as a side note, he further speculates that the Christian custom of having potluck dinners after the service may derive from Judaism of that time - Since it was strictly enforced that no food preparation was possible on the Sabbath, those services on Saturday night were often potluck too, with everyone cooking something up before heading to the service...
You then need to also deal with the Scripture that talks about not judging another on the feast days or sabbaths that they observe. One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind. (Romans 1:5) Thank you.
If you would kindly read up the page from Rom 1:5 you will find the context is having to do with fasting, not the Sabbath or the holy days that YHWH ordained.
My mistake, it’s Romans 14. But, yes, let’s look at the chapter:
1 Accept the one whose faith is weak, without quarreling over disputable matters. 2 One person’s faith allows them to eat anything, but another, whose faith is weak, eats only vegetables. 3 The one who eats everything must not treat with contempt the one who does not, and the one who does not eat everything must not judge the one who does, for God has accepted them. 4 Who are you to judge someone else’s servant? To their own master, servants stand or fall. And they will stand, for the Lord is able to make them stand.
5 One person considers one day more sacred than another; another considers every day alike. Each of them should be fully convinced in their own mind. 6 Whoever regards one day as special does so to the Lord. Whoever eats meat does so to the Lord, for they give thanks to God; and whoever abstains does so to the Lord and gives thanks to God. 7 For none of us lives for ourselves alone, and none of us dies for ourselves alone. 8 If we live, we live for the Lord; and if we die, we die for the Lord. So, whether we live or die, we belong to the Lord. 9 For this very reason, Christ died and returned to life so that he might be the Lord of both the dead and the living.
10 You, then, why do you judge your brother or sister? Or why do you treat them with contempt? For we will all stand before God’s judgment seat. 11 It is written:
“‘As surely as I live,’ says the Lord,
‘every knee will bow before me;
every tongue will acknowledge God.’”
12 So then, each of us will give an account of ourselves to God.
13 Therefore let us stop passing judgment on one another. Instead, make up your mind not to put any stumbling block or obstacle in the way of a brother or sister. 14 I am convinced, being fully persuaded in the Lord Jesus, that nothing is unclean in itself. But if anyone regards something as unclean, then for that person it is unclean. 15 If your brother or sister is distressed because of what you eat, you are no longer acting in love. Do not by your eating destroy someone for whom Christ died. 16 Therefore do not let what you know is good be spoken of as evil. 17 For the kingdom of God is not a matter of eating and drinking, but of righteousness, peace and joy in the Holy Spirit, 18 because anyone who serves Christ in this way is pleasing to God and receives human approval.
19 Let us therefore make every effort to do what leads to peace and to mutual edification. 20 Do not destroy the work of God for the sake of food. All food is clean, but it is wrong for a person to eat anything that causes someone else to stumble. 21 It is better not to eat meat or drink wine or to do anything else that will cause your brother or sister to fall.
22 So whatever you believe about these things keep between yourself and God. Blessed is the one who does not condemn himself by what he approves. 23 But whoever has doubts is condemned if they eat, because their eating is not from faith; and everything that does not come from faith is sin.
Sorry, Roamer, I do not see this ONLY referring to fasting, but in ALL things we should act by faith. Man was not made for the sabbath, but the sabbath for the man, our Lord said. We all NEED a day of rest, I agree, but we do not live under the Jewish law, but under grace. That “set-aside/apart” day (which the word “holy” means) is between us and God and no one else has the right to judge another on that.