not until 在强调句型中的用法

not until 引起的时间状语置于句首时，句子的主谓应部分倒装。由 not until 引导的时间状语从句位于句首时，主句应部分倒装，从句语序不变。如：

Not until 1998 did he return to his hometown.
直到 1998 年他才回到家乡。

Not until Father came back did we begin to have supper last night.

昨晚直到父亲回来，我们才开始吃晚饭。

注意：当 not until 引导的状语或状语从句用于强调句型时，句子的主语不倒装。如将上两句改为强调句应为：

It was not until 1998 that he returned to his hometown.

It was not until Father came back that we began to have supper last night.

not until或not···until意为“直到···才”或“在···之前不···”通常与非延续性动词连用，强调主句所表示的状态或情景从until所表示的时间才发生，主句必须是否定句，until与not同时位于句首时，主句和谓语必须倒装。
It was或is not until···
=It is或was+被强调部分+that+其他部分
例句：
I didn't get up until 7:00.

I couldn't speak until I was tow years old.