As I understand the gap theory, it is not about taking more than six days to create all things. The gap theory is about a gap of time in which the earth was formless and void.. then God created all things. The gap of time was between the creation of the earth that had full complete life, then there was destruction of that world, not of the planet and it's position in the solar system, but destruction like unto the flood of Noah, since there is the description of the waters and the Holy Spirit hovering upon it's surface.
So, the gap theory is talking about a former world system on the earth previous to the recreation of life, the garden of Eden, and the creation of Adam.
Have you heard that teaching?