There is no additional context to the Genesis account that would tell us that it is anything but a literal 7 day period. The only way to come to the conclusion that it is not a literal 7 day period is by disregarding what it plainly says.
It says the sun was created on Day 4. Therefore before Day 4 there could be no 24 hour 'day'.
Unless you bring an infinite and timeless God down to man's level of existence and insist that days 1 through 3 were 24 hour days.
Gen 2:9 And out of the ground made the LORD God to grow every tree that is pleasant to the sight, and good for food;
and
2:15 And the LORD God took the man, and put him into the garden of Eden to dress it and to keep it.
19And out of the ground the LORD God formed every beast of the field, and every fowl of the air; and brought them unto Adam to see what he would call them: and whatsoever Adam called every living creature, that was the name thereof.
20And Adam gave names to all cattle, and to the fowl of the air, and to every beast of the field; but for Adam there was not found an help meet for him.
You also have to believe that the trees and plants in the garden of Eden grew to full maturity in less than 24 hours.
You also have to believe that Adam named all the animals on earth in less than 24 hours.
Let's take a look at Day Six:
God created beasts, cattle, and wild animals.
God created Adam.
God planted a garden in Eden and caused it to sprout and grow.
God put Adam in the garden in order to cultivate it.
God brought all the birds, cattle and wild animals to the garden for Adam to name.
God caused Adam to fall asleep and created Eve from one of his ribs.
So with all this going on how could it be 24 hours?