Difference between ときがある and ことがある

Question

Someone just asked me the difference between 「ことがある」(when it means "there are times when") and 「ときがある」, and I actually couldn't answer since I have never really thought about this...

Could someone teach me the nuance between those two? thanks.

Answer 1

I am going to discuss two things that I feel might be of interest.

1) Explicit Meaning

2) Implied Frequency & Predictability

The differences are quite subtle. In fact, unless your friend is really approaching a native-level fluency, I might just show him/her @choco's answer and hide my own. Showing my answer could cause more confusion.

Explicit Meaning:

The difference is that while the expression 「ときがある」 already contains a time/frequency word in 「とき」, 「ことがある」 does not contain such an element at least explicitly.

In other words, 「～～ときがある」, all by itself, means "there are times when ~~.", "(Something) happens once in a while.", etc. just like one might expect the expression to literally mean. An additional frequency word would often be unnecessary, if not forbidden. If I said:

「ときどき食べすぎるときがある。」,

the redundancy should be "physically" clear. (I assure you, though, that native speakers sometimes do say something like that in informal settings.)

With 「ことがある」, however, it would actually sound better if you intentionally added a frequency word to it for clarity.

「ときどき食べすぎることがある。」

sounds 100% natural with no redundancy or a hint of awkwardness.

Implied Frequency & Predictability:

This is in no way a clear-cut rule or anything, but I feel as a native speaker that「ときがある」 would often tend to imply a higher frequency of the event than 「ことがある」 would.

In addition, 「ことがある」 would tend to express a higher degree of unpredictability of the event than 「ときがある」 would. There is this "as-a-matter-of-fact" kind of feeling associated with 「ときがある」.

There is a sort of an "element of surprise" expressed in 「ことがある」, at least more so than in 「ときがある」.

Answer 2

「ことがある」(when it means "there are times when") and 「ときがある」

I don't see much difference between:

ワインを飲んで頭が痛くなることがあるんです。
ワインを飲んで頭が痛くなるときがあるんです。

I think they practically mean the same thing. "There are times when~~" "sometimes / occasionally~~". To me, ときがある sounds a little bit more casual than ことがある.

Answer 3

This is a difference that I've been interested in myself for sometime.

The other day, I saw a children's education video (made for Japanese children) which specifically said the "〜したときがある” version was incorrect and ”〜したことがある" was correct. In all Japanese textbooks I have read, I have only seen こと used for this construction.

I found this page where a Japanese person is asking the same question.

The quick summary is that several people say using とき for this is just plain incorrect, and one person says it is a new expression young people have started using. The fact the children's video specifically highlights this grammar mistake makes sense if many young people have started using it.

Some other people say it might be a dialect of certain regions, and one person specifically says he/she has heard someone using it in a certain region. The question poster asks whether using とき this way is an expression particular to Tokyo, and while one answerer agrees with this, another person disagrees. (One person also debates what "Tokyo dialect" means since some consider their Japanese the "standard", though I won't get into this here).

Also, one person does say that the specific phrase "するときもある" would be acceptable.

So I think the short answer is that Japanese people will understand if you use 〜とき, however you should definitely stick with 〜こと to be safe.