この二つが王道の聞き方だと思います。"how long〜"という聞き方は「どれくらいの間」という意味です。"When did you" だと「[いつ](https://eikaiwa.dmm.com/uknow/questions/53271/)あなたはきたの？」という意味になります。
例：
A: How long have you been in Japan?
日本に来てどのくらいなんですか？
B: About two years.
2年くらいです。
A: When did you come to Japan?
日本に[来た](https://eikaiwa.dmm.com/uknow/questions/82084/)のはいつですか？
B: Two years ago.
2年前です。
All of the above questions are correct for asking the same questions - the length of time someone has been in Japan.
You can use a few others;
Have you been here long?
When did you first come to Japan?
Hope this helps
Jane:)
上の質問は全て日本にいる期間を尋ねるものです。
以下のも使えます。
Have you been here long?
ここにきて長いんですか？
When did you first come to Japan?
日本にはいつ来たんですか？
役に立てば幸いです。
Jane:)
A: How long have you been in Japan?
B: I have been here for 2 weeks.
This phrase can be used in a variety of ways.
"How long have you been apart of that company?"
"How long have you been studying Japanese?"
"How long have you been married?"
A: How long have you stayed in Japan?
B: I have stayed here for 5 days now.
A: How long have you lived in Japan?
B: I have lived here for 1 year.
A: How long have you been in Japan?
(日本に来てどのくらいですか？)
B: I have been here for 2 weeks.
（2週間です）
このフレーズはいろいろなバリエーションで言うことが出来ます。
"How long have you been apart of that company?"
(仲間と別れてからどのくらい経ちますか？）
"How long have you been studying Japanese?"
（日本語をどのくらい勉強していますか？）
"How long have you been married?"
（結婚してどのくらい経ちますか？）
A: How long have you stayed in Japan?
（日本にどのくらい滞在していますか？）
B: I have stayed here for 5 days now.
（今日で5日目です）
A: How long have you lived in Japan?
（日本にどのくらい住んでいますか？）
B: I have lived here for 1 year.
（1年間住んでいます）
Example
Friend: Hi, I'm John from London. I'm new in Japan.
Me: Hi, I'm Hiro. So, how long have you been in Japan?
Example
Friend: Hi, I'm John from London. I'm new in Japan.
Me: Hi, I'm Hiro. When did you arrive in Japan?
Hello :-) I hope this helps!
A) When did you arrive in Japan ?
*Arrive- reach a place at the end of a journey or a stage in a journey.
"we arrived at his house and knocked at the door"
B) How long have you been in Japan ?
* Long - referring to the time period
こんにちは :-) 回答がお役に立てば幸いです!
A) When did you arrive in Japan ?（日本にはいつ着いたんですか？）
*Arrive- 旅の最終又は途中の地点に到達すること
"we arrived at his house and knocked at the door"（彼の家に着いてドアをノックした）
B) How long have you been in Japan ? （どれくらいの期間日本にいるんですか？）
* Long - 時間の長さを指して
"How long have you been in Japan?" This asks them to tell you the amount of time they have been in Japan.
"When did you arrive in Japan?" This asks the person to tell you the date they arrived in Japan.
"How long have you been in Japan?" これは日本の滞在期間を尋ねています。
"When did you arrive in Japan?"これはいつ日本に到着したか尋ねています。
How long have you been here?
Have you been here for long?
How long have you been in Japan for now?
Are all suitable ways of enquiring how long someone has been in a destination.
How long have you been here?
こちらに来てどのくらいになりますか？
Have you been here for long?
こちらに来て長いですか？
How long have you been in Japan for now?
日本にはどれくらいいるんですか？
これらはすべて、その人がその場所にどれくらい滞在しているのかを尋ねる質問です。
How long have you been in Japan is a way to get a very specific answer. You will likely get a response which includes an exact figure e.g, I have been in Japan for 4 days.
If you ask it the second way a person might just say yes or no. Usually they will add an amount of time onto the end.
How long have you been in Japanは具体的な期間についての回答が返ってくる質問です。
例,（英文） I have been in Japan for 4 days.
（訳）私は今の所日本に４日間滞在しています。
二つ目の質問ではyesかnoの答えが返ってきます。
Yesかnoの後に滞在期間を言います。
So, how long ago did you get to Japan? - this is a casual way of asking when did they arrive in Japan
How long have you been living here? - this is one way of asking how long they've been living in a place.. it can refer to the country (if you are in the same country) or their home/apt (if you are currently inside of their home) since 'here' is vague, and it needs context to make sense
So, how long ago did you get to Japan?
（いつ日本に来たましたか？）
＊いつに日本に到着したのかを尋ねる、カジュアルな聞き方です。
How long have you been living here?
（どの位こちらに住んでいるんですか？）
＊国であったり、家の場所であったり、場所全般に対して使えるので、Here だけだと曖昧な場合は" Japan" など、地名や場所を指し示す言葉を使って補いましょう。
こんにちは。
さまざまな言い方ができると思いますが、例えば下記はいかがでしょうか：
・How long have you lived in Japan?
日本に住んでどれくらいになりますか？
・When did you come to Japan?
日本にはいつ来たのですか？
ぜひ参考にしてください。
日本 
イギリス 
アメリカ合衆国 
南アフリカ 
