back in the day 回到过去；早在一天；黄金年代；回头是岸

【例句】
But I remember back in the day, people were pretty excited about the T-shirt.
但是回忆以前，人们为T恤衫非常钟情。

My dad's always talking about how great everything was back in the day.
我爸爸总是讲过去的一切如何如何的好。