"it's a day when" 是一个表达特定情境或情况的固定结构。这个短语通常用于描述某一天发生了某些特别的事情或状况，它强调了这一天对说话者来说是重要的、具有特殊意义的一天。“It's a day when I finally got to see my dream job.”（这是我在梦想工作上终于见到我的一天。）it's a day when是什么从句？
it is / was +时间点when + 句子----------属于时间状语从句
When their victory came that day, all the people gathered on the city center square to celebrate
it.
It was already morning when they woke up
0