one day

何事: what sort of matter; unspecified matter

what sort of matter / unspecified matter

(rare) the first day of the month

one day, 24 hours / the daytime, the period from dawn until dusk / (figuratively) a short period of time / one day, someday, an unspecified day / the first day of the month

end, conclusion / end-of-life, death

to end, to finish, to quit / to be in a hopeless position

end; conclusion; finish / death; collapse; fall

何: interrogative pronoun; what

何か: something