Francis Schaeffer on the age of the Earth:
What does day mean in the days of creation?
The answer must be held with some openness. In Genesis 5:2 we read: “Male and female created he them; and blessed them, and called their name Adam, in the day when they were created.” As it is clear that Adam and Eve were not created simultaneously, day in Genesis 5:2 does not mean a period of twenty-four hours.
In other places in the Old Testament the Hebrew word day refers to an era, just as it often does in English. See, for example, Isaiah 2:11,12 and 17 for such a usage.
The simple fact is that day in Hebrew (just as in English) is used in three separate senses: to mean (1) twenty-four hours, (2) the period of light during the twenty-four hours, and (3) an indeterminate period of time. Therefore, we must leave open the exact length of time indicated by day in Genesis.
from Genesis in Space and Time, p. 59
Francis Schaeffer was a firm believer in the truthfulness of the Scriptures, and was open to understanding the opening chapters of Genesis as allowing an old age for the Earth. This wasn’t because he was some sort of compromiser, but because he saw it as a valid Biblical interpretation.
Grace and Peace