up till now
for+一段时间
ever since
表示次数的
1）It is the first / second time…. that…结构中的从句部分，用现在完成时。
It is the first time that I have visited the city.
It was the third time that the boy had been late.
2）This is the… that…结构，that从句要用现在完成时.
This is the best film that I've (ever) seen.
by+……时间