While a straightforward reading of the book of Genesis makes plain that human life is only 6,000 years old, the universe itself may be older. This can be inferred from the initial verses in Genesis 1 indicating that the Earth, and thus planets with gravity already existed.
|“||Genesis 1:1-2 ¶ In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.||”|
Furthermore, that the Angels had already been created may be inferred from Job 38:4-7:
|“||Job 38:4-7 ¶ Where wast thou when I laid the foundations of the earth? declare, if thou hast understanding. Who hath laid the measures thereof, if thou knowest? or who hath stretched the line upon it? Whereupon are the foundations thereof fastened? or who laid the corner stone thereof; When the morning stars sang together, and all the sons of God shouted for joy?||”|
If a day is defined, per Genesis 1, as one evening and one morning (v. 5), then it is technically possible to consider that vast amounts of time passed prior to the 4th day when the Sun was created. The word day is only used to refer to 24-hour days after the creation of the sun in Genesis 1:14. Prior to the creation of the sun it was simply defined as one cycle of darkness and light per Genesis 1:5. Nonetheless, this still cannot justify the theory of evolution's lengthy time spans for the creation of life itself, since animals were not created until the 5th day. (v. 24)
|“||Genesis 1:5 And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
Genesis 1:14-18 ¶ And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years: And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so. And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also. And God set them in the firmament of the heaven to give light upon the earth, And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good.
Nonetheless, Biblically-sound Gap Theory cannot justify a purely naturalistic Big Bang or evolution model over vast time scales. Genesis 1 makes clear that the creation of Earth as we know it happened within a single week composed of 24-hour days. During that time God formed the atmospheric boundary layer in the troposphere (vv. 6-8), continents and seas (vv.9-10), vegetation (vv. 11-13), and the stars throughout the universe (vv. 14-19). Even if one assumes the stars were "null and void" prior to this in the same way Earth was, allowing for the formation of planets and stars earlier, animal and human life are still of recent origin.
At best, Gap Theory can justify an early date of creation for planetary bodies themselves, but not for animal or human life. Vegetation, having been created on the 3rd day, could have survived an indeterminate amount of time before the Sun's creation depending on what the original source of light in vv. 3-5 was. It is likely that Jesus, the 'Light of the World' (John 8:12, 9:5) was the original source of light just as He will be the last:
|“||Revelation 21:23-25 And the city had no need of the sun, neither of the moon, to shine in it: for the glory of God did lighten it, and the Lamb is the light thereof. And the nations of them which are saved shall walk in the light of it: and the kings of the earth do bring their glory and honour into it. And the gates of it shall not be shut at all by day: for there shall be no night there.||”|