Hi. Please help. Let us say there is a person named John Doe, who served in the army from 1973 to 1976 and is making positive impacts as a business leader at a local communiy.

Hypothetical Situation 1: He is invited to speak at a community meeting as a speaker since the people in the community consider him as a role-model and want to hear from him. Here, I don't think present perfect is correct.

Now... we have Mr. John Doe, who served in the army from 1973 to 1976, and is contributing greatly to our society as a business leader ...

Hypothetical Situation 2: He is a candidate for President of a local veterans association and he is at a candidate dabate. Could he be introduced in this way? Here, I think present perfect is correct since it carries current relevancy. What do you think?

Next, we have Mr. John Doe, who has served in the army from 1973 to 1976, and is contributing greatly to our society as a business leader ...
AnonymousPlease help.
You have overlooked the most basic feature of present perfect tense usage, namely, that you cannot mention a specific time with it.

from 1973 to 1976 is a specific time.

Both cases require the simple past.

CJ
Hi. Thank you. Let us delete those time specific words, "from 1973 to 1976." What is your position on the appropriateness of the tenses in those two made-up situations. Thank you very much in advance for your help.
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AnonymousLet us delete those time specific words, "from 1973 to 1976." What is your position on the appropriateness of the tenses in those two made-up situations.
In that case either served or has served can be used in either situation. Since these are introductions, I would use has served in both cases because both situations are introductions to a group of people. Introductions are like resumes. They typically include mentions of past experiences with the present perfect tense.

CJ
Thank you for your help.