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We can use じゃなかったです for past tense, but can we replace the です with でした so that
it becomes じゃなかったでした? Why or why not?
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2016-03-06T03:52:08.120
32686
2016-03-19T14:46:56.350
2016-03-19T14:46:56.350
542
13761
question
grammar politeness tense
Past negative tense じゃなかったでした
No, you can't do that. じゃなかったです is a confusing form because it's a
colloquialism, and thus is only "grammatical" de facto. The proper form is
じゃありませんでした, or without contractions, ではありませんでした. じゃなかったでした is completely
incorrect and can't be used under any circumstances.
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2016-03-06T06:56:38.837
32691
2016-03-06T06:56:38.837
9596
32686
answer
The negative past forms are:

  1. なかった
  2. なかったです
  3. ありませんでした

In 1 and 2, the tense change is **already realised** by ない→なかった, and です just
acts as a helper to add politeness. なかったでした does not exist because です will not
inflect to show tense since it's just a politeness helper here.

In 3, the tense change is realised by でした, but note that in the case of
present tense, ありませんです does not exist because the politeness is already
accounted for by ます(manifested as ません here), so です is not required as a
politeness helper in the present tense.
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2016-03-06T09:28:51.253
32693
2016-03-06T09:28:51.253
542
32686
answer