Using Tenses 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.
I finished the Hollins project last week.
I have finished the Hollins project last week.
(That's when the ceremony occurred.)
(Incorrect!)
(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.

Use present progressive tense to describe ongoing projects.

See also:
Grammar: Simple Present Tense
Grammar: Present Perfect Tense

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