Why? How many days does it take to create the Earth?
When you look into a science book, you'll learn that according to our astronomical and physical observations gravity needed 9.1 billion years for creating the earth. You may calculate yourself how many days this took.
Thats because 'modern Protestantism' does not believe the Bible literally.
Most Protestants would object. They think that they are interpreting the bible more correct and literal than you, and that the idea of a 4000 BC creation is neither Christian nor biblical.
Don't you think it is a weak and cowardly for a religion to throw out whats contained in its Holy Book in order to 'modernize' and fit with science or to fit with society?
If a certain interpretation of the Holy Book does not fit with science, then the interpretation itself is weak, and not the the people who recognize that.
It requires extreme courage to change fundamental religious views. Protestantism was up to this challenge. Many parts of Christianity followed. Some still haven't found the courage to perform that step. Who is the coward here?