Thats when incoming...这种when表语从句，怎么样翻译和理解when的使用方法？

In 1919, President Woodrow Wilson had a stroke and his second wife Edith essentially ran the country for 18 months.

By that point, the 25th Amendment was long overdue

but it took the Kennedy assassination to get it written.

And it didn't get used by a president for another two decades when President Reagan had a 1985 surgery

but it got it's real test two years later.

That's when incoming Reagan Chief of Staff Howard Baker was urged to consider it after reports that Reagan was in mental decline.

请教老师，最后一句That's when incoming...这种when表语从句，怎么样翻译和理解when的使用方法？

That's when incoming Reagan Chief of Staff Howard Baker was urged to consider it after reports that Reagan was in mental decline.

that指代前句话的内容——it got it's real test。is在本句不是系动词，而是不及物动词，意为 take place, happen. when引导时间状语从句。

句子可翻译为：这发生在...的时候。