The use of the word "yom" in Genesis 1:1 is exactly the same as all the other places where "yom" is used to denote a 24 hour day.
I'll just point this out again. The days of Genesis are about a temple inauguration. It's not about the age of the earth.
Heaven and earth is God's temple. The Bible tells us this clearly.
Isaiah 66:1-2 NASB
[1] This is what the Lord says: “
Heaven is My
throne and the
earth is the
footstool for My feet. Where then is a
house [temple] you could build for Me? And where is a place that I may
rest? [2] “
For My hand made all these things, So all these things came into being,” declares the Lord.
When God rests on the 7th day, His resting place is on the throne. As is noted in many places in the old testament. It's His temple throne room.
Psalms 132:7-8 NIV
[7] “Let us go to his dwelling place, let us worship at his footstool, saying, [8] ‘Arise, Lord, and come to your
resting place, you and the ark of your might.
[13] For the Lord has chosen Zion, he has desired it for his dwelling, saying, [14] “This is my resting place for ever and ever;
here I will sit enthroned, for I have desired it.
The Lord is in His holy
temple; the Lord’s
throne is in
heaven; His eyes see, His eyelids test the sons of mankind.
Psalms 11:4
“Now then arise, Lord God, to Your
resting place, You and the ark of Your might; let Your priests, Lord God, be clothed with salvation, and let Your godly ones rejoice in what is good.
2 Chronicles 6:41
And every temple, when it's constructed, has a 7-day inauguration. It's right there in the Bible:
2 Chronicles 7:1 NIV
[1] When Solomon finished praying, fire came down from heaven and consumed the burnt offering and the sacrifices, and
the glory of the Lord filled the temple.
[5] And King Solomon offered a sacrifice of twenty-two thousand head of cattle and a hundred and twenty thousand sheep and goats. So the king and all the people dedicated the
temple of God.
[8] So Solomon observed the festival at that time for
seven days, and all Israel with him—a vast assembly, people from Lebo Hamath to the Wadi of Egypt.
And that 7-day celebration is when God enters His temple and takes up the throne:
2 Chronicles 5:13-14 NIV
[13] The trumpeters and musicians joined in unison to give praise and thanks to the Lord. Accompanied by trumpets, cymbals and other instruments, the singers raised their voices in praise to the Lord and sang: “He is good; his love endures forever.” Then
the temple of the Lord was filled with the cloud, [14] and the priests could not perform their service because of the cloud, for
the glory of the Lord filled the temple of God.
“But will God indeed dwell on the earth? Even heaven and the highest heaven cannot contain you, much less this
house [
temple] that I have built!
Hear the plea of your servant and of your people Israel when they pray toward this place; O hear in heaven your
dwelling place; hear and forgive.
1 King 8:27
As the glory of the Lord entered the
temple by the gate facing east, the Spirit lifted me up and brought me into the inner court; and behold,
the glory of the Lord filled the temple. While the man was standing beside me, I heard one speaking to me out of the temple, and he said to me, “Son of man, this is
the place of my throne and the place of the soles of my feet, where
I will dwell in the midst of the people of Israel forever. And the house of Israel shall no more defile my holy name, neither they, nor their kings, by their whoring and by the dead bodies of their kings at their high places,
Ezekiel 43:4-7
And that's what the 7-days of Genesis is actually about. It has nothing to do with science or geology or anything like that.