So I'm teaching my romance language-speaking students how to use English's present perfect… yeah I know, difficult battle. However one issue that I'm having trouble understanding myself is the usage between a couple of prepositions, namely for and in.
The classic prepositions that are taught are since and for. Ex:
- I have lived in New York since I was a kid.
- I have lived in New York for my whole life.
And honestly you can find hundreds of examples online and it's easy to explain / teach: for with time periods, since with points of time, blah blah blah…
My problem though is the rarely taught for-in distinction. Take for example:
- I haven't been here for a long time.
- I haven't been here in a long time.
Here I perceive a difference in meaning, however:
- I want to do something I have not done for a year.
- I want to do something I have not done in a year.
Here I can't hear any difference. (Can you?)
Furthermore sometimes only for works. Ex:
- We haven't known each other for a long time.
- We haven't known each other in a long time.
While other times only in works. Ex:
- This is the first time I've washed the dishes for days.
- This is the first time I've washed the dishes in days.
After doing a little bit or internet spelunking I found out that is may be linked to negation, but notice in my last pair of examples, there is no grammatical negation.
This is just a wild guess, but I think a revised definition for the usage of these three prepositions in present perfect sentences could be:
Since: is used with a starting point.
For: is used with a period of time when the action DOES happen.
In: is used with a period of time when the action DOES NOT take place.
What do you guys know about this? Both prescriptive and descriptive explanations accepted. I've also heard there may be a difference between RP and GA English… I just don't know.