This topic is what makes creationist so unbelievable. Seconds, minutes, hours, days, weeks, months, years, centuries are all relatively modern concepts and since humans didn't start writing until about 3100 B.C. being able to keep track of how long a year is was probably not possible (or highly irregular). That is one of the two parts of the bible that bug me. How did the people that first recorded the bible after centuries of the verbal version know how long a day was or know that Adam was over 900 years old. That makes calculating the length of a generation impossible let alone being able to pin down creation is only 60,000 years old.
When you also take into account that when the moon was first created it was much closer and earth had a much less stable rotation and wobble. The length of a hour and a day and a year have all changed since then (using our current calculation methods).
Not that I am anti religious but the scientific side of my mind says not religious text written by human hands can be taken word for word literally.