“as clear as day”别理解成“像白天一样清楚”，真实含义是一清二楚；显而易见；容易理解；昭然如日；肯定的。

【例句】
Although it’s written on the door as clear as day, people still don’t realize that this room is private.
虽然它显而易见，但人们还是不知道这个房间是私人房间。

Nobody can lie in painting, a universal language, for the truthfulness and depth of feelings in paintings are as clear as day.
绘画这种世界语无法撒谎，作品中感情的真假、深浅是一目了然的。