since,since+时间点/过去时态的从句，up to now,by now,so far“到目前为止”,in/over the last/past+时间段
?I have worked here for 8 years.
?I have worked here since 2004/eight years ago.
?Up to now/By now
we have learnt half of the book.
?I have never been to America.（现在完成时与次数连用）
?Great changes have taken place in China in the past ten years.
句型?It is +时间段+since+从句谓语用过去时
?It/This is the first/second time that+从句谓语用have done ?It/That was the first/second time that+从句谓语用had done ?这本书你借了多久了？（借书borrow a book/keep a book)
--How long have you __ the book?
--It is two weeks since I___ it.
A.borrowed B. Kept ?我参军两年了。（参军join the army/be in the army）
I have __ the army for two years.
It is two years since I ___ the army.
I ___ the army two
years ago. A.have been in B.have joined C.joined
?我感冒一个星期了。（感冒catch cold/have a cold） I __ a cold a week ago. I __a cold for a week. It is a week since I __ a cold.
a