by next year和by the end of next year

问题描述:

by next year和by the end of next year
它们有没有区别?主句的时态一样不一样?

by next year到下年
by the end of next year到下年底
比较:后者强调年末,时间概念明确,前者无具体时间,在合同中最好用后者.
时态是一致的.