  We argue that the neutrino halo, a population of neutrinos that have
undergone direction-changing scattering in the stellar envelope of a
core-collapse supernova (CCSNe), is sensitive to neutrino emission history
through time of flight. We show that the constant time approximation, commonly
used in calculating the neutrino halo, does not capture the spatiotemporal
evolution of the halo neutrino population and that correcting for time of
flight can produce conditions which may trigger fast neutrino flavor
conversion. We also find that there exists a window of time early in all CCSNe
where the neutrino halo population is sufficiently small that it may be
negligible. This suggests that collective neutrino oscillation calculations
which neglect the Halo may be well founded at sufficiently early times.
