[Lokean]

So that's a yes. The only sort of cumulative VP is once every summer, not monthly.

The point being, it doesn't actually matter what a religion thinks if there's 'real metaphysics' (mmm, oxymoronic!) involved. Nifelheim might consider winter months holy, but that's not going to change the fact that the nature of reality requires rituals on the summer solstice, at a place of metaphysical significance. It's not "Faster! We much rush to that particular little province so our god will receive the necessary blessing of the holy August holidays..."
It's "Faster! the conflux of ley lines is coming! Lay waste to the puny humans that would seek to control the power of the heavens!" If your god says 'go here, do this, or I shall be quite put out' you jolly well go and do it, even if summer does seem a funny time to do something for your god. The problem is, the religion's beliefs need not have any bearing on the matter of when and where junctures of mystical power occur.