I get this wrong every time. I always seem to translate this as "this day is pretty."
Wouldn't that be, "Nani kēia lā."?
This has been a no-fail trick for me so far: Every time I see "he" before a noun, I know it has to be "a/an" + noun.
That is because "he" is the word for "a/an"!
How would you say this day is beautiful?
Nani kēia lā.