When God acts on Day 4 to create the sun and moon to separate day from night, the stated purpose is very anthropocentric, very Israel-centric, and focussed on the worship of the God who creates.
How so? Well, the lights in the vault of the sky are there to “serve as signs to mark seasons, and days and years” (Genesis 1:14, NIV 1984). But ‘seasons’ speaks to more than just phases of the year - the term is associated with the cultic calendar, with the set times for festivals. You can’t go far into the Old Testament without seeing that the overwhelming use of the term is for the tent of meeting and the feasts associated with it. Hence the NIV 2011 translation of ‘seasons’ in Genesis 1:14 as ‘sacred times’ - appointed times for feasts and festivals.
Sun and moon are created not simply as markers of the changing seasons for practical purposes but, deliberately, to allow for sacred times - the hallowing of time, the ordering of engagement with the God who created all things. Those markers are clearly tied to the provisions of the Old Testament (and therefore created with OT Israel in view), for as Paul notes in Colossians 2:17, those festivals and days were “a shadow of the things to come; the reality…is found in Christ.”
And so, in the new heavens and earth, when all things have been made new, we discover that there will be no sun or moon (Rev. 21:23): no regulation of festal times, for all time will be festal and filled with the fulness of the presence of God; no longer will there be seasons, for the tree of life will bear fruit every month (Rev. 22:2), its leaves for the healing of the nations, bathed in the light of the reconciling God and of the Lamb.
