It is two years since I last met him.
21. It is + time when…
我到电影院时已经八点钟了。
It was 8 o’clock when I got to the cinema.
22. It is + time before…
不久我们就会再见面的。
It won’t be long before we can meet again.
23. It is…that…
我最珍视的是友谊。
It is friendship that I value most.
24. It is + n / adj + that / to do…
每个人都必须懂得如何使用计算机
It is a must that everybody should know how to use computers.