Question

by the end of的用法

Answer 1

by the end of 表示“(从之前的某个时间点开始)到结束为止”，前面用完成时态，如

1. They had finished their work by the end of last Friday. 过去完成时

2. They will have finished their work by the end of tomorrow. 将来完成时
   

at the end of 表示“在结束的那个时间点”，前面不用完成时态，可用一般过去时、一般将来时等，如

1. They finished their work at the end of last Friday. 一般过去时

2. They will finish their work at the end of tomorrow. 一般将来时