Suppose you were talking to your friend, in a casual conversation. Friend: Was that your father whom we saw yesterday at the school? You: Yes, that was my father.
I'm quite confused whether to use "that is my father" or "that was my father".
I feel it should be "that is my father", because the question establishes the fact that my father was seen in the school yesterday and be it today, tomorrow, a week or a month later, he's still going to he my father.