If one reads genesis from 1:1 to 1:31, from a ego, or geocentric view, then then the impression that is received is that God created the earth in six days and rested on the seventh.
I do not know where the suggestion has come from that the Lords day is like thousand of earth years.
By putting those two bits of information together we get 6000 years and then there is the seventh day that adds to the equation.

If you understand the information from a different perspective then you will come to a different conclusion.
First of all, “genesis” deals with the origin of the universe, not the origin of the planet Earth.
Second: The word “earth” in genesis has the equivalent meaning to the modern words “Higgs field.”
Third: A volume of space that has light, contains energy, a volume of space that has absolutely no energy is dark in all wave lengths.
Fourth: Day is full of energy, the “Night” referred to in genesis represents a volume of space that contains no energy of any kind.
Fifth: In genesis, the “evening” and “morning” refers to a first instance of a cyclic decreasing and then increasing of the energy, or light, content of the universe.
In other words a day in the universe is longer than a day on Earth.
At least in my opinion.