I know that んだった and んじゃなかった can be used to say "Should have done" and "Shouldn't have done". I am wondering, however, if they can be used as a past version of んだ Take for example this conversation:

A friend: You never spend time with me

You: 忙しいんだ (The thing is, I'm busy)

Now I try with んだった

A friend: You never spent time with me

You: 忙しいんだった (I was busy, that was why)

Is this incorrect or correct?

Much appreciated

Daniel Safari

  • Yes, this is correct.
    – istrasci
    Feb 6, 2013 at 18:15
  • 3
    忙しいんだった>>忙しかったんだ in that situation
    – user1016
    Feb 6, 2013 at 18:48

2 Answers 2


I'm going to offer a different answer.

I think it does not work the way you think.

んだ is a statement, which works as emphasis of what is being said/thought now. It can not be used the same way in the past.

It's just that I'm busy.

has as past tense

It's just that I was busy.


It was just that I was busy.

cannot be expressed in Japanese the same way. 忙しかったんだった is certainly most cumbersome. In English, "It's just that" can be conjugated to "It was just that" to make an explanation about something in the past, which is not how it works in Japanese.



I could imagine saying this (to myself) if I accidentally bothered someone, after being told to leave them alone because they were busy.

"it was the case that [he?] is busy"

"(oh, I forgot,) [you] were busy" (and still are)

You can't say something like あ、忙しかった for this purpose -- that implies they're no longer busy.


This fits the situation you're describing.

  • Always nervous answering questions of Japanese usage instead of interpretation, hope this is correct...
    – Hyperworm
    Feb 6, 2013 at 18:31
  • What you're saying seems very logical to me. Feb 6, 2013 at 18:39

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