It is time you did something (注意这里要用过去式)

方法1：
It's time to go home / It's time for us to go home.

方法2：
It's late. It's time we went home.
这里用went却表示的现在而不是过去时态。

奇怪吧。可是这就是语法规则，必须记牢了。

语气上，是批评的，表达说，早该走了。还墨迹啥啊。

还有更强烈的批评

It's about time / It's high time
Jack is a great talker,  But it's about time he did something instead of just talking.