Using tenses correctly

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.

I met Mr. Flinders last year at a Convention in Little Rock. I have met him since last year. I have known him since last year.

(Specific time) (Incorrect!) (Correct!)

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.