Tense and aspect in 'since' clause

Question

Consider:

1. I have not heard from him since he lived here. (Activity)

2. How long is it since you were in London? (State)

3. John is now with his parents in New York city, it is already three years since he was a headmaster. (State)

4. He has studied very hard since he came to our school. (Accomplishment)

5. I have learned to be dangerous upon points of honour since I served the Spaniard. (Activity)

6. It is three weeks since you have been here. = It is three weeks since you were here.

These are all taken from a paper written by a Chinese college teacher who teaches English.

He said different verbal aspects in these since clauses could lead to different interpretation:

#1 implies some time ago he left here and I haven't heard from him since then.

#2 again implies you haven't been living in London and I ask for how long you haven't been living in London.

#3 implies he resigned as a headmaster three years ago.

#4 is easy. He has been studying hard in our school.

#5 is different than #1, 2, 3. It means I have learned to ... since I began to serve the Spaniard and during the time I have served the Spaniard.

#6 is an idiosyncrasy. He said that in the "It's some time since clause" pattern the use of present perfect or the past simple makes no difference in meaning: You haven't been here for three weeks.

I'm not very confident about his explanations, especially #6. I think at least in #6 the choice of tense does have an influence over the meaning.

And why would #1, 2, 3 have the opposite meaning from #5?

I'd like to hear what a native speaker would say about it.

Answer 1

First, keep in mind since X can have two meanings:

• Equivalent to because X or because of X: I'm at the store now since we're out of food.

• Equivalent to from the time X: I have been at the store since early morning.

When the second meaning is used, the tense of the main clause must be in the past because the whole point of using since is to express how much time has passed after something has started. So this sentence is ungrammatical:

How long is it since you were in London? (State)

but anyone will understand what you mean if you say this.

Similarly, 3 should be this:

John is now with his parents in New York city, it has already been three years since he was a headmaster. (State)

and 6 should be this:

It has been three weeks since you have been here

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Part of selecting an aspect (i.e. whether or not you use have) is whether or not a specific time or duration is indicated, and since does both A) fix the start of an action at a specific time and B) can specify the duration, e.g. from that point in time until now.

These guidelines for past continuous versus past perfect continuous provide an example where since might affect the aspect:

If you do not include a duration such as "for five minutes," "for two weeks" or "since Friday," many English speakers choose to use the Past Continuous rather than the Past Perfect Continuous. Be careful because this can change the meaning of the sentence. Past Continuous emphasizes interrupted actions, whereas Past Perfect Continuous emphasizes a duration of time before something in the past. Study the examples below to understand the difference.

Examples borrowed from that same article:

He was tired because he was exercising so hard.

This sentence emphasizes that he was tired because he was exercising at that exact moment.

He was tired because he had been exercising so hard.

This sentence emphasizes that he was tired because he had been exercising over a period of time. It is possible that he was still exercising at that moment OR that he had just finished.

So you cannot say "He was tired because he was exercising so hard since 2:00pm" because since defines a period of time.

Answer 2

I have not heard from him since he lived here.

?We have not communicated since he moved away.
"... since he's lived here" would mean "in the time between his arrival and the present".

How long is it since you were in London?

When were you last in London?

John is now with his parents in New York city, it is already three years since he was a headmaster.

Three years have passed since John stopped being a headmaster.

He has studied very hard since he came to our school.

He has been studying very hard since his arrival here at our school.

I have learned to be dangerous upon points of honour since I served the Spaniard.

This is not contemporary English.

It is three weeks since you have been here.

I guess this means "You were here three weeks ago." I'd say "It's been three weeks since you were here."