Misplaced(?) に in たった4週間の間に毎日3Lの水を飲み続けた女性の変化がヤバすぎ！


Related: [Particles after time expressions like
"三週間"](https://japanese.stackexchange.com/questions/38529/particles-after-
time-expressions-like-%e4%b8%89%e9%80%b1%e9%96%93)

> 【衝撃】 たった4週間の間に毎日3Lの水を飲み続けた女性の変化がヤバすぎ！皆さん、普段の生活の中で意識して”水”を飲...

  1. Can you explain what's wrong with the に in 「たった4週間の間に毎日3Lの水を飲み続けた女性の変化がヤバすぎ」?

and/or

  2. Can you modify/rewrite it to make it better?




There is nothing wrong with this Japanese sentence, although it sounds
informal. The key difference is " _for_ three weeks" (continuously) vs "
_within/in/after_ three weeks". To say the former you don't need any particle
after 週間:

>   * 3週間日本にいる be in Japan _for_ three weeks
>   * 3週間水を飲み続ける keep drinking water _for_ three weeks
>   * 3週間のあいだ水を飲み続ける keep drinking water _for_ three weeks  
>  (sounds a bit redundant, but it can be heard)
>

Compare:

>   * 3週間のあいだに変化する change _within_ three weeks
>   * 3週間以内に変化する change _within_ three weeks
>   * 3週間で帰宅する return home _in_ three weeks
>   * 3週間後に改善する improve _after_ three weeks
>

In this sentence, the focus is the _change_ happened to this person _only
within_ four weeks, so saying たった4週間のあいだに is okay. Without the word 変化,
[*]たった4週間の間に水を飲み続ける ("keep drinking water only within four weeks"?) doesn't
really make sense.

I feel 「○週間の間【あいだ】に」 (=within ○ weeks) is not wrong but a bit redundant and
clumsy. When you write formally, I would suggest you use ○週間以内に or ○週間で
instead.

