你是那么专注于一项活动，以致忘了时间。

You become so deeply absorbed in an activity that you lose track of time.

《柯林斯英汉双解大词典》

我不能把时间浪费在这种无聊的活动上。

I can't waste time on such frivolities.

《牛津词典》

她只用自己一半的时间从事政治活动。

Only half her time is occupied with politics.

《牛津词典》

Suppose that most times and most activities were death free, but certain activities introduce the possibility of dying.

假设大部分时间和大部分活动都是死亡免疫的，但某些活动,会引起死亡的可能性。

耶鲁公开课 - 死亡课程节选

In another example, you can use a "when" question in order to ask about the timing of a specific event.

在下面这个例子中，你可以用When 问句来询问一个具体活动的时间。

When 课堂 - SpeakingMax英语口语达人

What we are hearing were periods of quietness and periods of a lot of action potentials.

我们听到的是一段寂静,然后是可能出现很多活动的一段时间。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选