I saw this sentence on a Japanese teaching site:

The incident occurred last week

I feel very uncomfortable with the に on 先週. This post and this post seem to back up my discomfort. Is this sentence ungrammatical/unnatural or am I missing something?

  • 1
    Can you tell me which Japanese teaching site?
    – Jimmy Yang
    Apr 15, 2021 at 23:59
  • 1
    @JimmyYang It was Duolingo. It has a lot of stuff which seems unnatural to me, but it's good for improving my terrible listening skills so I keep ploughing through it. Apr 16, 2021 at 0:10

2 Answers 2


As a native speaker, I also feel uncomfortable with 事故は先週に起こった, which can be said to be a little unnatural but probably cannot be said to be ungrammatical. 先週 plays the role of an adverb in this sentence, so its natural sentence will be:

  • 事故は先週起こった。

But as a writer, I would like to avoid this, because I don't like the awkward sequence of Chinese characters of 先週 + 起. So I like this sentence transcribed like this with the use of punctuation marks.

  • 事故は(、)先週、起こった。
  • 先週、事故は起こった。(very natural to me)

This point might be trivial for other Japanese, but I am always wondering how to use this kind of noun phrase used as an adverb. In order to avoid this (discomfort), I prefer the following to the above sentence.

  • 事故は先週のあいだに起こった。(a little longer, but very natural to me)

After answering this question, I hit upon the following sentence.

  • 先週起こった事故は、すごかった。

This sentence with に in it is, no doubt, grammatical and quite natural. I have no idea of the cause of the difference in naturalness and grammaticality between this and the above sentence (事故は先週に起こった).

  • 1
    Very interesting point about consecutive kanji lining up in that way. For me, that's perhaps the most informative aspect of this answer (and the use of commas).
    – A.Ellett
    Apr 16, 2021 at 14:26

文法的には間違ってはないと思います。 使い方によっては不自然に感じられるかもしれません。 おそらく日本人が 「事故は先週に起こった」 と聞けば、「先週」という部分が強調されているように感じると思います。つまりいつ起こったのかを強調したいときには、「先週」に「に」をつけるのは自然です。 例えば誰かに 「事故はいつ起こったのか?」 と質問されて、それに答える文として 「先週に起こった」 というのならしっくりくる表現です。

先週を強調しない言い方なら 「先週、事故が起こった」 と言うと不自然には感じません。

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