Although the "gap theory" is not as popular as it used to be, there is still a significant body of Bible expositors who teach that this theory is the best way to deal with the alleged long ages of Earth history. For example, the Scofield Bible says in its note on Genesis 1:1:

Thirty days hath September,
April, June and November;
February has twenty-eight alone,
All the rest have thirty-one,
Except in Leap Year, that's the time
When February's days are twenty-nine.

Bible skeptics have long raised this objection to the Flood story. How could one man and his sons travel to all corners of the globe collecting all the pairs of animals to preserve them through the coming Flood? How did he even know about them? It's a serious question and deserves a careful answer.

There is a wonderful promise found in one of David's psalms, as follows:

The words of the Lord are pure words: as silver tried in a furnace of earth, purified seven times. Thou shalt keep them, O Lord, thou shalt preserve them from this generation for ever (Psalm 12:6-7).