87436
I encountered the examples of 去る.

  * 今を去ること２０年前
  * 今を去る２０年前
  * 東京を去ること200キロ

If I understand them correctly, they mean a certain amount in space/time away
from a particular point. 「今を去る２０年前」makes perfect sense to me, but I am puzzled
by the 「こと」 in 「今を去ること２０年前」 and 「東京を去ること200キロ」. What does こと mean here? What
role does it have in the phrases?
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2021-07-11T09:34:07.517
87429
2021-07-11T14:52:26.073
38770
question
grammar meaning
What is the こと in いまを去ること20年前?
This is a fixed pattern used with a time length, a distance, etc. It sounds
dramatic as compared to simple 20分待つと, etc.

  * オーブンに入れて待つこと20分、美味しいケーキが焼けました。  
Twenty minutes in the oven and ....

  * 自宅を出て車で走ること15km、隣町のショッピングセンターに到着した。  
Fifteen kilometers after leaving home, and ...

  * 遡ること2日、この部屋では別の事件が起きていた。  
Two days back, ...

  * 考え続けること実に3時間、我々はついにひとつの結論に達した。
  * ベルを鳴らすこと10回、いまだに返事はない。

Basically this こと should be a nominalizer, but unfortunately, I could not find
this usage in my usual dictionaries, nor could I find this pattern in well-
known JLPT learning sites.
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2021-07-11T14:14:03.813
87436
2021-07-11T14:52:26.073
2021-07-11T14:52:26.073
5010
5010
87429
answer
Practically speaking, you can take _[clause]_ + こと + _[numerical expression]_
to mean 'Now I talk about things when I do _[clause]_ _[numerical exp]_. It is
a rhetoric to arouse listener's attention.

Your Examples:

  * 今を去ること20年前 : (Now I talk about) 20 years ago
  * 今を去る20年前 : I think this can be think of the version where こと is dropped
  * 東京を去ること200キロ : I went 200km from Tokyo, then you know what?, (something interesting should follow)

Also さかのぼること20年(前) means '(Going back) 20 years ago'

Duration:

  * 研究すること10年 : I've been investigating for 10 years

Also number of times can be used:

  * 繰り返すこと100回 : I repeated it 100 times
  * 失敗すること100回 : I failed 100 times

Sorry this doesn't directly answer your question, but こと in these construction
does not have concrete meaning, but rather functions as a glue between
_[clause]_ and _[numerical exp]_ so to speak.

===

I found a long discussion (most probably with no conclusion) on this
construction.

[https://www.atmarkit.co.jp/bbs/phpBB/viewtopic.php?topic=10367&forum=3&start=16](https://www.atmarkit.co.jp/bbs/phpBB/viewtopic.php?topic=10367&forum=3&start=16)
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2021-07-11T14:23:53.987
87437
2021-07-11T14:23:53.987
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87429
answer