你落后于时代的英文表达是 "You are behind the times." 或 "You are out of date." 。
"Behind the times" 这个说法有两种解释。第一种意思是某人或某事物没有跟上时代的发展，过时了。例如：
"My phone is so old, it's behind the times." (我的手机太老了，落后于时代。)
"The company's business model is behind the times. They need to innovate to stay competitive." (公司的商业模式落后于时代。他们需要创新以保持竞争力。)
第二种意思是某人或某事物在过去比较流行，但现在已经过时了。例如：
"That hairstyle is so behind the times. No one wears it anymore." (那种发型太过时了，现在没人再穿了。)
"His music collection is full of oldies. He's really behind the times." (他的音乐收藏里全是老歌。他真的落后于时代。)
"Out of date" 也有类似的意思，指某事物已经过时了。例如：
"This map is out of date. Some of the roads have changed." (这张地图过时了，有些道路已经改变。)
"The information in this textbook is out of date. We need a newer edition." (这本教科书的信息过时了。我们需要一个新版本。)
"Behind the times" 这个说法有两种解释。第一种意思是某人或某事物没有跟上时代的发展，过时了。例如：
"My phone is so old, it's behind the times." (我的手机太老了，落后于时代。)
"The company's business model is behind the times. They need to innovate to stay competitive." (公司的商业模式落后于时代。他们需要创新以保持竞争力。)
第二种意思是某人或某事物在过去比较流行，但现在已经过时了。例如：
"That hairstyle is so behind the times. No one wears it anymore." (那种发型太过时了，现在没人再穿了。)
"His music collection is full of oldies. He's really behind the times." (他的音乐收藏里全是老歌。他真的落后于时代。)
"Out of date" 也有类似的意思，指某事物已经过时了。例如：
"This map is out of date. Some of the roads have changed." (这张地图过时了，有些道路已经改变。)
"The information in this textbook is out of date. We need a newer edition." (这本教科书的信息过时了。我们需要一个新版本。)