(the following is not a direct answer to your question, but I think it might be interesting from the point of view of language learning.)
When it comes to attributes, it is not always necessary to use past tense in Chinese, even if the phrase you have in mind should be said in past tense in your own language.
For example, you met someone years ago and now a third person asks you about your opinion of this person. In English you can say something like " He was very nice." or " He was a gentleman.". When you translate these sentences into Chinese, you say "他人很好" "他很紳士的一個人", no adverb of time which indicates the past tense is needed. If you add one of these adverbs in the sentence, "他(曾經/以前/過去/那時)是個很好的人", it means that at this moment you are aware of the fact that he has changed, or he is dead, so your previous judgment does not correspond to the reality.
I think this shows that when your way of thinking is formed in a language like Chinese, a judgment is often saved in the form like essence of a person or of a thing, which is no longer in the time. When I discuss philosophy with friends who do not speak Chinese, at the beginning they think I reason in a rather instinctive, subjective way, because in their eyes, I always tend to isolate a fact from its surroundings. It takes me years to spot why do they say so. Well, this reasoning process itself is unconscious of course, and it is not about being right or wrong : it's just a way of thinking.
I always have problems with the past tense in English and in French. Now I realize that there is a substantial difference in the way of thinking, the way we make judgments and how we keep them in the form of language. It's more than mere mechanical grammatical difference...
The above is just my personal opinion. Hope it could be useful to you in some way. :)