Not to get to religious but you have to consider what "time" is when taking into consideration of the Genesis story. We experience time by the rotation of the earth and its revolution around the sun. So how can one measure time before time even existed?
In short time is an illusion based on our perspective here on earth. As you move towards the speed of light time ceases to exsit. As you get physically further from earth time for you slows while it keeps going on earth.
In short time if you were to measure a year in space and a year on earth they would not be the same. Time is relative based on your perspective.
So to answer your orginal question no it would not be 24 hours. Genesis is definitely an allegory for somthing quite deeper about human existence and the zodiac.
well put.