Some Bible-believers understand the days in Genesis were twenty-four hour periods but between the literal days there were vast amounts of time, possibly billions of years. They view the days in Genesis as literal and sequential but not consecutive. God's creative activity took place in a series of steps separated by long ages. This is also known as progressive creationism.
Occurred Between
The creative acts occurred largely
between the literal days. Each day introduced a new creative period. Evidence for this viewpoint is that the Book of Genesis is organized on a genealogical scheme that involves life spans that are sequential but overlapping.
Earth Is Ancient, Days Are Solar
This theory attempts to wed the twenty-four hour literal day with the geologic ages. Both theories are true according to Progressive Creationism. This position allows the earth to be ancient while still keeping to the interpretation that the term day in
Genesis 1 was a solar day. Therefore we have six literal days in Genesis that are sequential but not consecutive.
Difficulties With Gaps Between The Days
While the Gap Theory argues for one gap, progressive creationism argues for number of gaps. Therefore the problems are also multiplied.
Also, there is no evidence that there were any gaps between the days in the first chapter of Genesis. This has to be read into the text to harmonize Genesis with modern science.
Furthermore there are no other examples in Scripture where we find gaps between literal days.
All of these factors makes the theory suspect.