如果你是單單想描述你在 1956 年被辭退,那麼用 simple past tense 則可以了:
I was fired by ABC Company in 1956.
如果你想強調你曾經被辭退,並有意義帶到現在,並配合其他句子,你可以用 present perfect tense,例如:
I have been fired by ABC Company since the manager came. (And I am still unemployed now.)〔我明白你的例子是已經退休,因此沒有什麼必要用 present perfect tense。〕
因此,如果只是簡單敍述,無必要用 perfect tense,用 simple past tense 就可以了。