"We are clearly told in the book of Genesis that God created the
heavens and the earth in a very short sequence of time, six literal
days.
The Hebrew text is grammatically put together using a specific
verbal construct called a waw consecutive that defines historical narrative. Each individual day (yôm) is further defined by the nouns evening (‘ereb) and morning (bôqer) and an ordinal number (e.g., the sixth day, yôm hašiššîy [Genesis 1:31]).
If this weren’t clear enough, the six-day creation is affirmed twice in Exodus: “For in six days the LORD (Yahweh) made the heavens and the earth” (20:11, 31:17).
Furthermore, we are told in these verses and also in Genesis 2:2 that God rested on the seventh day, which Hebrews 4:4 cites in the New Testament: “And God rested on the seventh day from all His works.”
This is where we get our seven-day calendar week, the only
demarcation of time not built on a solar or lunar cycle." ICR