day and night; always
Example sentences
彼は弁護士になるために日夜勉強に励んだ。
He studied day and night with a view to becoming a lawyer.
彼は日夜働いて過労になった。
He worked day and night and overworked himself.
彼は自分の家庭が楽に暮らせるように日夜働いた。
He worked day and night so that his family could live in comfort.