I learned it from this guide, detailing 「だめ」,「いけない」 and 「ならない」constructions.

I was able to assume that the past-tense of "I must not do" is て-formはだめだった (correct me if I'm wrong), but how can I do the same for things I must do? I guess maybe it's negative て-formはだめだった, but as Tae Kim says, that's super long and thus would probably sound weird if I used it outside formal situations. Up to now, I've used the "replace なくて with なくちゃ" slang form, but how would I put that into past tense?

I was thinking about using 行けないだった, but that's even longer than だめだった so it's a no go, I'm guessing. Any advice?

  • Can you give the English past-tense construction you're trying to express in Japanese? My first guess would be that you're trying to express "I must not have done X" ("must" here in the "required" sense rather than the "certain" sense), but that is a very weird hortative construction - when would you ever say that in English?
    – senshin
    Sep 18 '15 at 3:46
  • 1
    Side note: when using いけない in the grammatical sense like you are here, it is typically written purely in kana. 行けない would generally only be used for the negative potential form of 行く "to go".
    – senshin
    Sep 18 '15 at 3:49
  • I was just thinking about it in a hypothetical sense, because it was the only one I couldn't figure it out, but now that you mention it, you're totally right. Thanks for the help with いけない, too. Sep 18 '15 at 4:45
  • Well, actually one more thing. Perhaps this isn't the right construction, but I was talking about things I had to do. For example, "I had to do my homework." I would translate this as, 「宿題しなくてはだめだった。」Is this the right construction for that sentence? If it is, I'd say "I have to do my homework" is 「宿題しなくちゃ」, but I'm not sure how to express past tense. Sep 18 '15 at 4:51

You don't really have to do anything special- just put the final verb (adjective) in the past tense.

学校まで走らなければならない - I have to run to school
学校まで走らなければならなかった - I had to run to school

This works with all three of the constructions you mentioned.

ならない = ならなかった
だめ(だ) = だめだった
いけない = いけなかった

Of these, I see ならなかった the most by far, but the other two are possible.

Your suggestion of 「いけないだった」 is not possible, because it is ungrammatical. The past tense of an i-adjective is -かった; you can't append -だった. So it should instead be 「いけなかった」.

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