Unspecified point in the past

　　I have been to Shanghai three times before. 这句话其实并没有明确的时间状语，故而时间状语可以被认为是从“说话者”出生到说话的当下。如此一来，现在完成时肯定是最佳的时态选择了。

　　I went to Spain three times in 2008. 与上句话相比，这句的时间状语非常具体，所以用一般过去时或者过去完成时更为贴切。

　　An action that occurred in the past, but has a result in the preset

　　We cannot find out our luggage. Have you seen it?

　　丢行李是之前就发生了的事情，这件事情对现在也有明显的影响。所以用have you seen来提问，比较恰当。

　　Talking about general experiences.

　　Have you ever been there before (in your life)? 与“一”中的情景类似。看上去没有明确的时间状语，那么就可以根据句意理解为：in your life。

　　Evens that recently occurred (just)

　　I’ve just eaten my lunch. 此句强调刚刚吃过。

　　Events that have occurred up to now (yet)

　　They have not arrived yet. And we must wait. 前一句强调的是他们直到现在还有到的状态，所以用现在完成时比较准确。

　　Events that occurred before you expected (already)

　　I’ve already graduated from college. Already在句子中通常被译作：早已，早前，已经。用来强调事情在预期之前已经发生。

　　Events that began in the past and haven’t changed (for, since)

　　Mike has worked here for 3 years. Mike has worked here since three years ago.这个现在完成时与后面的时间状语相互配合，强调从那时起直到现在谓语动词一直处于某种状态。

　　毫无疑问，隔壁老樊的《我曾》其实大部分都是在向人诉说自己的人生遭遇。用现在完成时，没毛病。