I could totally see Dark enjoying a solar eclipse. He‘d probably have some special ritual prepared to commemorate the occasion. It wouldn’t be a nice kind of ritual though, like our modern holidays. Probably more along the lines of the kind of stuff the Aztecs did back in the day.
I could also imagine His more supernatural night-based powers (like the dream-walking from HoD, for instance) would get a boost from the darkness. And, because He’s naturally nocturnal (being a creature from a dark world), this would also be a busy day for Him.
A solar eclipse is basically the Hellgod’s Christmas morning, where He gets whatever He wants today for being so good (at being bad, that is). And we mere mortals need to fucking HIDE.