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The perfect tences are used with for, together with a phrase dnoting a period of time, to indicate the duration or continuance of an action or state of affairs up to the time specified by the context or situation; 11a I've lived (or I've been living) in London for twelve years. (up to present time) 11b By the end of 1970, I'd lived (or I'd been living) in London for two years. 11c By the end of 1995, I shall have lived (or I shall have been living) in London for seventeen years. The present perfect and past perfect tence are used with since, together with a phrase or clause denoting the beginning of an action or state of affairs, to indicate the continuance of that action or state from the time specified until the present time, or until the time specified in the past;
12b At the age of 40, he decided to move to the north of England. He had (up to that time) lived in London since he was 21, and had some misgivings about moving. Since is also used as in 12a and 12b after the construction ; It's + period of time; 13a It's ten years since I met him. However, the present perfect is also occasionally found after since in such sentences: 13b It's ten years since I've met him. While there is little, if any, difference between these two sentences, we could perhaps make a distinction in emphasis (or focus of interest) by means of a paraphrase: a I last met him ten years ago. (the speaker is thinking primarily or the time of the last meeting) b I haven't met him for ten years. (the speaker is thinking of the length of time that has alapsed) |