“And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness. And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day” (Genesis 1:3-5).
I am a creationist. I personally believe that God created all things in heaven and earth in six literal 24-hour days. A proper understanding of creation is essential, since it is the foundation upon which all the doctrines of God rest. Sadly, some in Christendom have sought to erect an elaborate system known as the day-age theory to accommodate the geologic timetable of billions of years. But does this position pass the Berean test?
Those who subscribe to the day-age theory believe that the Hebrew word “day” (yom) can refer to a 24-hour day or a long period of time. This is true! For example, the day of the Lord is an extended period of time which covers well over one thousand years. Consequently, the context must always be consulted to ascertain the duration of time under consideration. Of course, those who defend this position teach that the days of the Genesis record quite literally cover millions and millions of years, which conveniently accommodates evolution.
Interestingly, when the Hebrew word yom is used with a number, it always refers to a 24-hour day, without exception. In regard to the Passover God instructed Moses, “Seven days shall ye eat unleavened bread; even the first day ye shall put away leaven out of your houses: for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel” (Ex. 12:15).
Would we conclude otherwise that the “first day” here is anything other than a normal day? Furthermore, when perimeters are set on the term yom, such as “the evening and the morning,” as found in Genesis 1:4, this limits the day to 24 hours.
But perhaps the most conclusive evidence that each day was 24 hours is found in Exodus 20:11: “For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the LORD blessed the sabbath day, and hallowed it.” Here Moses uses the term yamin, the Hebrew plural for “days,” which exclusively speaks of 24-hour cycles.
If the Holy Spirit had intended to convey that the days of creation were “eras,” He would have used the used the Hebrew olam, which is defined as “indefinite time.” We accept by faith that God is sovereign and all-powerful; therefore, it was a small matter for Him to speak all things into existence in six days (Psa. 33:6-9). source