It is time 后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)，其意為“(早)該干某事了”。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修飾：

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

與其他的虛擬結構不同，該結構不能在該用 was 時而用 were。如：

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