短语"That'll be the day"通常表示说话者对某个不太可能发生的事件表示怀疑或讽刺。它可以用来表示不相信对方说的话，或认为某事很难实现。 例如，假设一个经常迟到的朋友向你保证明天一定会准时到，你可以用这个短语表示怀疑说："That'll be the day! 你从来没准时过。"这表示你相当怀疑你的朋友是否真能做到他所说的。
例句
"John is going to quit smoking," "That will be the day!"
"约翰说他要戒烟了","鬼才信呢"
When he finally cleans his room, that'll be the day!
等他终于打扫了自己的房间，那天估计得等到猴年马月了！
You say you're going to start working out every day? That'll be the day.
你说你打算每天都去健身？我看那天什么时候来都是个问题。
She promised to pay me back next week, but that'll be the day.
她承诺下周还钱给我，但我觉得那天可能永远不会到来。
They're talking about reducing taxes—well, that'll be the day!
他们谈论着减税——呵，我看那天可能永远不会实现！
He claims he's going to run a marathon without any training. That'll be the day!
满分语法 