Using Tense Appropriately

Use simple past tense to describe something that wholly occurred at a specific time in the past:
|
I graduated from NYU in 1998. NOT: I have graduated since 1998. |
(That’s when the ceremony occurred.) (Incorrect!) |
|
I finished the Hollins project last week. I have finished the Hollins project last week. |
(Specific time) (Incorrect!) |
Use present perfect tense to describe something that has been in effect from a certain point in the past until now. Be careful! Some verbs are used for specific actions; others are used for conditions that cover lengths of time.
Use simple present tense to describe facts.
I work for IBS Corporation.
He’s a sanitation engineer.
I am responsible for orienting new employees.
She answers company correspondence.
Use present progressive tense to describe ongoing projects.
I am developing new software.
She is teaching the hearing-impaired.
We are building a new mall in East Heights.
See also:

English Greetings & Phrases
English Pronunciation
English – Introductions
Rosetta Stone – English
Speak English as a Second Language
Learning English – Lesson One