住んでいた時 or 住んでいる時

Question

In this question, there is a sentence

私はローマに住んでいた時に子供でした。

My question is: do we need to consider relative tense here?

Can we say 住んでいる時 to mean that the event that I was living in Rome (A) and the then fact that I was a child (B) happened simultaneously (at least living in Rome didn't come before being a child)?

In this link, I found two example sentences

ご飯を食べている時、山田さんがうちへ来ました。

ゆうべ寝ている時、地震がありました。

Both use 〜ている時 instead of 〜ていた時 to mean "was doing something". So why do we use 住んでいた時 rather than 住んでいる時 to mean "was living"?

Answer 1

Some key points to consider when analysing your sentences:

1. Using the terminology of the Dictionary of Japanese Grammar series, your sentences are of the format S1 toki S2 (Sentence 1 とき Sentence 2).
2. According to that dictionary's explanation (p493 of 'A Dictionary of Basic Japanese Grammar'), when S2 is past tense and S1 expresses a state, you can use either past or nonpast in S1.
3. The verb 'live' is usually considered to be a stative verb (a verb that expresses state), at least in English (here, for example).
4. Therefore, since S2 is past (でした) and S1 expresses a state (住む), the verb in S1 can be either past (住んでいた) or nonpast (住んでいる). The meaning is identical for the phrases, according to their definition.

5. While your examples are grammatically correct, it would still be more natural to use the sentence 子供の時、ローマに住んでいました, as pointed out by another user. This construction emphasises that you are talking about a period of time in childhood. The 'living in Rome' time period is a subset of the total 'childhood' time period, not vice versa. As an analogy, consider how a similar restructuring might sound in English:

(A) I lived in Rome and I was a child.
(B) I was a child when I lived in Rome.

These are not direct translations of your sentences but the point is that show that while both are grammatically correct, Sentence A sounds strange because of the emphasis on living in Rome. Sentence B sounds natural because the relationship between the elements is correct.

6. The rules are different if the S1 expresses an action.

Answer 2

I am not a Japanese grammar expert but just a native Japanese speaker.
I think you can say 「ローマに住んでいる時、子供でした。」.

ローマに住んでいた時、子供でした
ローマに住んでいる時、子供でした

I personally think there is no difference between the meanings.

However, as the comment of the original question mentioned, the sentence 「ローマに住んでいる時、子供でした。」is a little bit wired even though it is grammatically correct.

「子供の時、ローマに住んでいました」is I think most natural way to say it.
Or if you want to put 「子供でした」at the end of the sentence, you can say 「ローマに住んでいた(る)時は、子供でした。」

The reason why I feel the original sentence is wired is I think that

1. A part before "、" is much longer than the rest of the sentence(or sentence after "、" is too short compare with the former part).
2. Usually, the information "you were a child at the time" is less important than the information "where you lived in your childhood". So If you add "は" after "時", I can smoothly understand the information that "You were child at the time" is main theme of this sentence and I can feel the sentence more natural