OK, *lots* to deal with!
1) Sunset - yeah, I was wondering about that: sunrise, noon and midnight all covered, it made sense that this would also end certain enchantments. Given the religious 'day' in Judaism etc starts at Dusk, I was thinking that Theurgic enchantments would end then.
2) Is it specified that only the owner can let someone in? Because we are all *residents*. Further, for purposes of ownership, scripturally the planet was given to Man in Genesis, so even if some Power is needed for the invite, Bless This House should be sufficient, as the character has faith that yes, they do own the world/day. (Oh, to pre-empt a quibble, time/space used interchangably in scripture, thus the English word 'world' may be translating either 'Kosmos' or 'Eon').
3) Dawn gets tricky because it is both a threshold *and* the beginning of sunlight, and sunlight hurts enchantments. That would be why it is the most obvious.
4) Do we have info on whether crossing a threshold destroys enchantments? Because IIRC Dresden has an enchantment that he can't even take out of his house.