It is time 後的定語從句用虛擬語氣

從句謂語通常用過去式表示現在或將來，有時也用過去進行時或“should+動詞原形”(較少見，且should不能省略)，其意爲“(早)該乾某事了”。如：

I think it's time you went to bed. 我想你該睡覺了。

It's time we went [were going, should go]. 我們該走了。

I think it's time they were taught a lesson. 我想現在該給他們一點教訓了。

注：time前有時有about和high脩飾：

I think it's high time that she made up her mind. 我想她該拿定主意了。

與其他的虛擬結搆不同，該結搆不能在該用 was 時而用 were。如：

It's time I was in bed. 我該上牀睡了。(不用were)