For what its worth this is what God of the Bible said about the Lords Day and being a holy convocation.
The Lords Day in God's own Words- the only one in the Bible
He claimed as His
Isa 58:13 “If you turn away your foot from
the Sabbath,
From doing your pleasure
on My holy day,
And call
the Sabbath a delight,
The holy day of the Lord honorable,
And shall honor Him, not doing your own ways,
Nor finding your own pleasure,
Nor speaking
your own words,
Exo20:10 but
the seventh day is the Sabbath of the Lord your God.
What He claimed as a holy convocation or church
Lev 23:3 ‘Six days shall work be done,
but the seventh day is a Sabbath of solemn rest, a holy convocation. You shall do no work
on it; it
is the Sabbath of the Lord in all your dwellings.
What Jesus kept as a holy convocation
Luke4:16 So He came to Nazareth, where He had been brought up.
And as His custom was, He went into the synagogue on the Sabbath day, and stood up to read. What He read from is the Book of Isaiah if you keep reading in this passage
What His church and apostles kept as a holy convocation, just as Jesus quoted from and predicted
Isa 56:6 “Also the sons of the foreigner
Who join themselves to the Lord, to serve Him,
And to love the name of the Lord, to be His servants—
Everyone who keeps from defiling
the Sabbath,
And holds fast My covenant—
7 Even them I will bring to My holy mountain,
And make them joyful in My house of prayer.
Their burnt offerings and their sacrifices
Will be accepted on My altar;
For My house shall be called a house of prayer for all nations.”
Why we see both Jews and Gentiles and all people coming together to hear the word of God every Sabbath in the NT
Acts 13:14
But when they departed from Perga, they came to Antioch in Pisidia, and went into the synagogue on the Sabbath day and sat down.
Acts 13:27
For those who dwell in Jerusalem, and their rulers, because they did not know Him, nor even the voices of the Prophets which are read every Sabbath, have fulfilled
them in condemning
Him.
Acts 13:42
So when the Jews went out of the synagogue, the Gentiles begged that these words might be preached to them the next Sabbath.
Acts 13:44
On the next Sabbath almost the whole city came together to hear the word of God.
Acts 15:21
For Moses has had throughout many generations those who preach him in every city, being read in the synagogues every Sabbath.”
Acts 16:13
And on the Sabbath day we went out of the city to the riverside, where prayer was customarily made; and we sat down and spoke to the women who met
there.
Acts 17:2
Then Paul, as his custom was, went in to them, and for three Sabbaths reasoned with them from the Scriptures,
Acts 18:4
And he reasoned in the synagogue every Sabbath, and persuaded both Jews and Greeks.
And what continues on forever as a holy convocation but instead of worshipping Him in spirit, it will be in person.
Isa 66:23 “
For as the new heavens and the new earth
Which I will make shall remain before Me,” says the Lord,
“So shall your descendants and your name remain.
23 And it shall come to pass
That from one New Moon to another,
And from one Sabbath to another,
All flesh shall come to worship before Me,”
says the Lord.
What Paul was referring to
Heb 10: 25 not forsaking the assembling of ourselves together, as
is the manner of some, but exhorting
one another, and so much the more as you see the Day approaching.