Part of the description of the hallow spell includes the following effect (emphasis mine):
First, celestials, elementals, fey, fiends, and undead can't enter the area, nor can such creatures charm, frighten, or possess creatures within it. Any creature charmed, frightened, or possessed by such a creature is no longer charmed, frightened, or possessed upon entering the area. You can exclude one or more of those types of creatures from this effect.
Say a creature is already charmed, frightened, or possessed by a listed creature type, and then the hallow spell is cast on an area that includes the creature. Is the charm/fear/possession effect ended, suspended, or unchanged when the spell is cast?
In other words, is casting this spell on the area such a creature is in enough to end one of these effects? Or must the creature leave and reenter the spell's area to achieve this?