From one month to the next
and from one Sabbath to the next,
all people will come to worship me,
says the LORD.
Isaiah 66:23 NET
Q: Why SABBATH in the New World?
A: Just like at the 1st creation, so too at the 2nd (new, recreation of the earth) a memorial is established as it was in the beginning as God originally designed it to be
And he that sat upon the throne said, Behold, I make all things new.
Revelation 21:5
Q: Why come month to month?
A: To eat of the Tree of Life.....apparently a monthly need
In the midst of the street of it, and on either side of the river, was there the tree of life, which bare twelve manner of fruits, and yielded her fruit every month: and the leaves of the tree were for the healing of the nations.
Revelation 22:2