(This is a total digression, so apologies)

My mind instantly answered that with "bright", which is what you get when you combine the sun and moon radicals to make 明(https://en.wiktionary.org/wiki/%E6%98%8E)

Anyway, that question is not without reasonable answers. "Full Moon" might make sense too. No obvious deterministic answer, though, naturally.

FTR the Full Moon was exactly 5 hours ago (It's not without humour that this conversation occurs on the day of the full moon :)