当然，很多产品明码标注着过期的时间，但是有的产品并没有。

Sure, many items explicitly state expiration dates, but some don't.

youdao

这个Expires HTTP头包含页面过期的时间，这样就可以避免浏览器在页面过期时间之前发送版本检查的请求。

The browser can safely not check for new versions until the expire date has passed. Setting this up in Apache is easy.

youdao

了解不同食物的“最佳食用日期”和“过期时间”，并正确烹调它们是很重要的。

It is important to know "best-before" and "use-by" dates of different foods and cooking them properly.

youdao

And one of them will be filmed, too, so that if you can't actually make any of the times not to worry, that video will go online sometime Tuesday in plenty of time for Friday's pset deadline.

其中一门课程也会被拍成录像，所以你们万一没有时间也不用担心,那个视频在周二会放到网上去,直到周五过期，这其中还是有充裕的时间的。

哈佛公开课 - 计算机科学课程节选