By the time
1.表示将来的时间.
主句用将来完成时,而从句用一般现在时来表示将来的动作.
如:I will have finishied the work by the time my father comes back.
2.表示过去的时间.
主句用过去完成时,而从句用一般过去时.
如：He had built a lab for himself by the time he was 12 years old.
by the end of
“到.末”,多指时间,常用于完成时态,也用于将来时态.
By the end of last month they had planted 10,000 trees.
如：到上个月月底他们已经栽了一万棵树.
请采纳