Word Choice – Usage of ‘Since’, ‘For’, and ‘In’

prepositionspresent-perfectusageword-choice

Which of these is grammatically correct?

1. a) He has been working under my direct supervision since the last two years

1. b) He has been working under my direct supervision for the last two years

2. a) He has not met her since a very long time

2. b) He has not met her in a very long time

Which of the above are correct?
Are all of them correct? My friend says 1.b and 2.b are correct, but I am not sure. Or is this an American English and British English thing? (He mostly goes by American English)

Best Answer

1b) and 2b) are correct.

You could correct 1a) as:

He has been working under my direct supervision since two years ago.

and 2a):

He has not met her since long ago.

Since as used here points to a specific time, not a time span as in your examples.
See the definition since senses 4 and 5.