Before adding a year to the creation narrative it must be established, by a biblical account, that thirteen cycles of nineteen years each was factually God’s method of tracking time. What was the bible event that shows the Metonic cycle to be the structure that God used to mark time? It was the worldwide flood, and the record of the length of time it lasted.
It is through Noah’s time log of the flood year that God has preserved His system of measuring time. It is through its compiler Moses that Noah’s time log has been preserved and it is God’s way of showing how time is recorded throughout the bible.