First, it is part of the Church’s extraordinary magisterial teaching that God:
…creator of all visible and invisible things of the spiritual and of the corporal . . . by his own omnipotent power at once (simul) from the beginning of time created each (utramque) creature from nothing, spiritual and corporal namely angelic and mundane and finally the human, constituted as it were, alike of the spirit and the body (DZ 428)
These words were formulated in 1215 as infallible teaching on Creation by the Fourth Lateran Council, many centuries before the multi-million year hypothesis of the earth’s age was advanced by geologists. There can be no doubt that the authors of the Council declaration were not expecting their words to be interpreted other than in a context of creation in no more than the six days as taught by Sacred Scripture, and by the Fathers of the Church to whom they turned as authority. The significance of the expressions “at once” and “each” (simul and utramque respectively in Latin) in this regard are discussed further on.