We happened to be at the station when it happened.

当此事发生时我们碰巧在车站。

youdao

He was 14 years old when it happened.

这件事情发生的时候，他14岁。

《牛津词典》

It had been the end of the school year when it happened three years ago, only a few days after my fourteenth birthday.

那还是三年前的事，当时学年就要结束，我的十四岁生日刚刚过去几天。

youdao

said the gray-haired woman. "You see,I was nurse to the boy when it happened,and for years afterward I worked in the family.

VOA: special.2010.05.15

I knew...when it happened, a lot of people had died.

我知道……它发生的时候，死了很多人。

911事件的影响 - SpeakingMax英语口语达人

When that happened it would destroy the economy.

当这种现象发生时，将会摧毁经济。

耶鲁公开课 - 金融市场课程节选

When it happened again a few weeks later, Andrews decided to take the statue down.

FORBES: Collateral Damage

Tourist Theresa Bastiman-Davies was on the lift with her eight-year-old son when it happened.

BBC: Rescue at Lecht

When it happened, Compaq was trapped in a typical 1999 incumbent's dilemma, beholden to the old sales channel.

FORBES: THE HUMAN ROLE