Peter gave an altar call in Acts 2. Paul told believers not to neglect their church meetings. Believers can meet any day or time of the week as they feel led. All very biblically sound.
I would disagree with these characterizations. What happened in Acts 2 was not an altar call as we would think of it today.
The ones that were there were "devout" men:
Act 2:5 And there were dwelling in Jerusalem Jews, devout men, from every nation under heaven.
They were there to observe one of the Lord's Holy Days, Pentecost:
Act 2:1 When the Day of Pentecost had fully come, they were all with one accord in one place.
They were not neophytes when it came to the God of Israel. They were well versed in scripture. They knew and believed in a coming messiah. What they didn't believe was that Jesus was that messiah. This was the point of Peter's sermon...to let them know that Jesus was the messiah and that he was expecting them to enter into a personal covenant with God and to enter into that covenant by repenting (changing their lives and thoughts totally), be baptized and receive the holy spirit. They knew 90% of what it takes to be a Christian because they had the scriptures that revealed Christ.
Modern altar calls seem to be mostly a spur of the moment, emotional thing that is often aimed at those who know absolutely nothing about scripture or the commitment they are making. "Giving your heart to Jesus" is okay to say when it's understood in the larger context of the new covenant. But someone getting baptized without understanding that is simply someone getting wet...imho.
As far as meeting any time of the day or week it's true....believers can. However there are absolutely days that the Lord commands his followers to assemble on.
Lev 23:1 And the LORD spoke to Moses, saying, Lev 23:2 "Speak to the children of Israel, and say to them: 'The feasts of the LORD, which you shall proclaim to be holy convocations, these are My feasts.
The "Lord" (the messiah, Christ) says that he has feast days. And on those feast days he expects the children of Israel (which included modern day Christians) to assemble and worship on.
I understand that many have been TAUGHT that Christian don't have to do this. But that is almost entirely the result of an anti-Jewish hatred in the Roman empire that arose beginning in the first century due to a series of revolts against Rome by Judea. It was decided by the Roman church that Christians should not keep the same days as Jews. This is all historical fact and can be found by looking at the canons of various early church canons. The hatred of Jews is obvious...but because a bunch of Jew hating men said we shouldn't observe the Lord's Holy Days is no reason to disobey God himself.
Believers can meet any day or time of the week as they feel led.
And believers can also fast and pray for 40 days in preparation for Easter, and call it "Lent" if they like.
Stop using one set of standards for what is "Biblical" where Catholic beliefs and practices are concerned, and a different set of standards for yourselves.