What length of time does a day mean in Genesis 1?

Do these verses suggest that time prior to the lights created at this point in the creation was not based on earths orbit around the sun and therefore the days of creation are of different periods of time than our 24 hour day?

Then God said, “Let there be lights in the sky to separate the day from the night. They will be signs and will mark religious festivals, days, and years. 15They will be lights in the sky to shine on the earth.” And so it was. 16God made the two bright lights: the larger light to rule the day and the smaller light to rule the night. He also made the stars. 17God put them in the sky to give light to the earth, 18to dominate the day and the night, and to separate the light from the darkness. God saw that it was good. 19There was evening, then morning—a fourth day.