The figure the afternoon watch salutes is a case study in how liturgy preserves what theology forgets. Apam Napat, grandson or child of the waters, was a great god of the common Indo-Iranian past: the Rig Veda hymns him as a golden radiance dwelling in the waters, and some scholars have seen in him an ancient deity of the fire born in water, lightning or the gleam on a river, whose paradoxical nature fascinated the early poets.
In the developed Zoroastrian system, where Ahura Mazda's supremacy reorganised the pantheon into created yazatas, Apam Napat kept an unusual title, ahura, lord, shared with only the greatest beings, a fossil of former rank; the tradition's texts give him the epithet of the swift-horsed and credit him with holding the royal fortune, the khvarenah, safe in the depths of the sea when it fled from usurpers, one of the great images of Iranian myth. Yet he has no cult feast of his own and little narrative; what he has, permanently, is the afternoon. Five times a millennium of days, whoever prays the Uzerin Gah names him, and the naming has outlasted empires, migrations and the loss of almost everything else once believed about him. Historians of religion cite exactly this case when they argue that ritual is the most conservative stratum of a tradition: doctrines about Apam Napat withered, but the watch that greets him has not missed an afternoon in something like three thousand years.