いつここに来ましたか vs ここに来ていつですか

Question

I want to ask "When did you come here?". Are both of these ways of saying it correct or are they wrong? Which one would you use and are there differences in their meaning? Is there maybe a third way to say it that you would suggest?

いつここに来ましたか

ここに来ていつですか

Answer 1

×ここに来ていつですか is incorrect.

So in English you have two different ways to convey this type of information:

1. I came here 3 months ago.
2. I've been here for 3 months.

And there are two different ways to ask about it:

1. When did you come here?
2. How long have you been here?

Note that you have to choose the correct interrogative. "When" obviously does not work in Sentence 2. (×"When have you been here?" is ungrammatical.) And this is exactly why ここに来ていつですか is an incorrect Japanese sentence.

Apparently, you already know there are also two ways to say this in Japanese:

1. 3か月前(に)ここに来ました。
   ^{(に can be dropped in casual speech)}
2. ここに来て3か月です。
   ^{(literally, "I came here and it's been three months.")}

As you know, turning them into questions is a simple process in Japanese. Just replace the part being asked with an appropriate interrogative, and add か at the end of the sentence:

1. いつここに来ましたか。
2. ここに来てどのくらいですか。

But note that いつ does not work in the second sentence! It's because "when" and "how long" are two different types of questions. To ask about a time span (i.e., "how long") in Japanese, you have to use どのくらい or どれくらい, not いつ. Alternatively, you can use 何か月 ("how many months"), 何年 ("how many years"), 何時間 ("how many hours") and so on.

ここに来て何年ですか。

The difference between the two is small, but the latter using どのくらい would sound more natural when you focus on the experience during the period.

See:

• "How long" in Japanese

Answer 2

Literally, They both mean "When did you come here?", but there are minor difference.

This is my personally feeling of the phrases:

1. I'm surprised that you are here, or complaining that you shouldn't be here, or kind of asking why you are here. It can be tell by tone of the speaker.
2. I already know that you have been here for a while, asking for the exact time you reach.

And the second is a little wired, following is a better one:

ここに来ったのはいつですか