So, I'm pretty damn sure that all the various timers and the like for NMs reset when there's a maintenance. Thus, all the various kings would be on day 2 now.
My friend Kelvanis is reporting from Dragon's Aery (I asked him to take a screenshot, so he'd hopefully post it soon) that Nidhogg just popped. But Nidhogg can't pop on day 2... right? I'm confused.