可以(指SINCE后的从句要用一般过去时）,如
It's three years since he came here .
如果SINCE后接过去的时间点,一般是用现在完成时,不用过去时,如
He has studied here since two years ago.
可以(指SINCE后的从句要用一般过去时）,如
It's three years since he came here .
如果SINCE后接过去的时间点,一般是用现在完成时,不用过去时,如
He has studied here since two years ago.