It is time 后的定语从句用虚拟语气

从句谓语通常用过去式表示现在或将来，有时也用过去进行时或“should+动词原形”(较少见，且should不能省略)，其意为“(早)该干某事了”。如：

I think it's time you went to bed. 我想你该睡觉了。

It’s time we went [were going, should go]. 我们该走了。

I think it’s time they were taught a lesson. 我想现在该给他们一点教训了。

注：time前有时有about和high修饰：

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

与其他的虚拟结构不同，该结构不能在该用 was 时而用 were。如：

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