Past to Present
Present Perfect
Present Perfect to Express Past to Present
The present perfect connects an action or state which began in the past and to the present moment in time.
I've bartended in three restaurants with mini-bars.
I've built three lunch rooms for the school district.
We haven't worked from those recipes for very long.
Positive Form:
Subject + have + past participle + (object(s))
I've been shopping at Safeway since I moved to this neighborhood.
Negative Form:
Subject + have + not + past participle + (object(s))
Alan hasn't taken requests here for very long.
Question Form:
(Wh?) + have + subject + past participle + (object(s))
How long have you worked with a dietician?
Present Perfect to Express Duration
When an action begins in the past and continues into the present moment we use the present perfect. This use of the present perfect expresses duration over time FROM the past moment TO the present moment.
Example:
I've bartended in three restaurants with mini-bars.
I've built three lunch rooms for the school district.
We haven't worked from those recipes for very long.
Contrast to the Present Simple
The use of the present simple expresses activities that occurs on a regular basis, such as habits and routines.
Example:
Business travelers don't fly on weekends.
The production center usually closes at seven o'clock.
In contrast, the use of the present perfect expresses actions that take place over time beginning in the past and coming into the present moment in time.
Example:
The daily rate has remained stable for three years.
We haven't worked from those recipes for very long.
Use of 'For', 'Since' and 'How long'
Use 'for' with the present perfect or present perfect continuous to indicate the duration of an activity or state.
The daily rate has remained stable for three years.
Those tour operators have worked at Universal Studios for thirty years.
Use 'since' with the present perfect or present perfect continuous to indicate a specific point in time an activity or state began.
Jane has provided our furnishing since January.
He has lunched in the employee dining room since taking over the company in January.
'How long' is used in questions to ask about the duration of an activity or state.
How long have you worked without computer access?
How long have you worked with a dietician?