85949
1. 

> A「お昼休みなのに忙しそうだね」
>
> B「午後から会議があるんだ」
>
> A「ずいぶんゆっくりしてるけど、大丈夫？」
>
> B「あっ、そうか！今日は午後から会議が **あったんだった** 」

  2. 

> A「今日一緒にご飯に行かない？」
>
> B「ごめん、今日は彼女との予定があるんだ」
>
> B「ごめん！さっき外食する約束をしたけど、今日は別の予定が **あったんだ** 」

Here are two dialogues. What would be the difference between あったんだった and
あったんだ?
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2021-04-02T12:49:45.057
85909
2021-04-04T04:07:43.557
2021-04-04T03:43:49.643
5010
36662
question
grammar modality
Difference between あったんだった and あったんだ
In such cases, there are two relevant differences to consider:

  * is a piece of information known to the speaker or not?
  * who does the information come from?

In the first scenario, in which two co-workers talk about a conference, B
already knew that a conference was to take place on that particular day. They
simply seem to have forgotten and are now re-establishing this knowledge. In
that case, the original information about the conference came from A and is
now re-stated by B.

In the second scenario, the information that B already has plans is new
information to A. Therefore, it is in the present tense, as B is offering this
new piece of information to A just now.
CC BY-SA 4.0
2021-04-03T09:24:11.947
85923
2021-04-03T09:24:11.947
43455
85909
answer
This use of た is called modal-ta or 発見のタ. There are a number of questions
related to this on this site.

  * [Non conventional usage of the past tense](https://japanese.stackexchange.com/q/40733/5010)

> "fixing (or updating) one's previous knowledge/expectation" seems to be the
> key

  * [Usage of plain i-adjectives or た form (悪かったｖ悪い、良かったｖいい etc）](https://japanese.stackexchange.com/q/21347/5010)

> It is used when one's expectation has just matched or failed to match
> reality.

  * [Conjugated word + んだ vs nonconjugated word + conjugated んだ](https://japanese.stackexchange.com/q/60788/5010)

In Dialog 1, B is updating his own knowledge, and that's why the sentence ends
with the modal-ta. But 会議があったんだった sounds a little redundant to me. 会議があるんだった
is equally correct and probably more common.

In Dialog 2, B is trying to update A's knowledge by telling what is already
known to B, so the sentence must not end with the modal-ta. 別の予定があるんだ and
別の予定があったんだ are equally correct, but the latter contains a modal-ta before the
end of the sentence to update A's knowledge; it implies "(I know) this is not
what you've expected".
CC BY-SA 4.0
2021-04-04T04:07:43.557
85949
2021-04-04T04:07:43.557
5010
85909
answer