God wasn't limited to 144 hours when creating the world out of nothing and His first creative act might have begun with a bang.
Creationism is opposed to atheistic evolution that claims matter is eternally self-subsisting. But if matter answers the question of its own existence, then by definition, it would be God.
Creationism isn't married to biblical fundamentalism, however, which asserts God created everything in exactly six 24-hour periods totaling 144 hours. Genesis chapter 1 does speak of six days in which God created all things including man. And Genesis 2:2 further relates that "God ended his work" and then "rested on the seventh day."
But as pre-Vatican II catechisms teach, this "'seventh day' is still going on." This means God is allowing nature to take its course without creating anything new. The seventh day, therefore, has lasted from the creation of Adam and Eve until now — far longer than 24 hours.
Fundamentalists don't realize the English word "day" as used in the creation narrative is actually translated from the Hebrew word yom. This is the same word used in such familiar phrases as Yom Kippur — the Day of Atonement and Yom Yahweh — the Day of the Lord.
The traditional catechism further notes the word "'day' may stand for a day, a week, a month, a century, or any indefinite period of time."
Biblical fundamentalists further ignore solar data that shows stars predated the earth and geological data that shows layers of geological time existed between prehistoric species and mankind. But supernatural or revealed truth doesn't violate natural or scientific truth as truth is truth.
Genesis 1:3 relates, "And God said: 'Be light made.' And light was made." Pope Pius XII personally believed this initial Divine act resulted in what's called the Big Bang. During the remaining five days of creation, that possibly lasted millions of years, God allowed nature to take its course while sequentially creating all living species as recorded in Genesis.
Find out what St. Thomas said about creation in season two of Church Militant's Premium show Right Reason—St Thomas, The Summa Theologica and Creation.