(Friday is too late. I need it in advance of Friday)
(周五就太晚了,最迟周四晚上)
这里我们把by和before放在一起来比较一下它们两个词的区别
来理解它们正确的用法
If you want the job to be ready on Friday morning, you would say
如果你要求在周五早上的时候工作是完成了的,你应该说
Please do this before Friday
If you need it to be done either before or during Friday, you would say
如果你要求工作在周五或之前完成,你应该说
Please do this by Friday
In other words, using by is inclusive, it means do this on any day up to and including the day specified. Using before is non inclusive, it means that I expect it to be done when I arrive on Friday morning.