Campare When ... ? ( + past simple ) and How long ... ? ( + present perfect ) A : When did it start raining? B : It started raining an hour ago / at 1 o'clock. A : How long has it been raining? B : It's been raining for an hour / since 1 o'clock. We use both for and since to say how long something has been happening. We use for when we say a period of time. (two hours, six weeks etc.) - I've bee..
