Ultrafast X-ray absorption spectroscopy offers elemental specificity and in principle access to the natural time evolution of valence excitations when studying electronic and structural configurations of molecules and materials. I will present time-resolved X-ray absorption spectroscopy simulations of pyrazine including wavepacket dynamics in both the valence- and core-excited state manifolds. We discuss the validity of the widely used short-time approximation which neglects the nuclear dynamics following the X-ray probe transition. We further demonstrate the impact of an explicit description of the electric field and explicitly calculate the effect of an increasingly longer excitation pulse on the observed photo-triggered wavepacket dynamics.