両フレーズとも、「[今](https://eikaiwa.dmm.com/uknow/questions/53431/)、夏休み中です。」という意味になります。
「夏休み」は、summer breakまたは、summer vacationと表すことができますが、私はアメリカ在住ですが、summer vacation の方をネイティブの方は良く使っているような気がします。
「[〜まで](https://eikaiwa.dmm.com/uknow/questions/51832/)夏休み」と伝えたい場合は、
I'm on summer vacation until ~. (例：I'm on summer vacation until the end of this month.)
I'm on summer break until ~. (例：I'm on summer break until the end of this month.)
少しでもお役に立てれば幸いです。
ありがとうございました。
Well, context is always key, no matter which language you are speaking, and in this case, the context will dictate the time of year it is and the time you are speaking. If it's summer and you are on vacation, then it is clearly, a summer vacation - so no need to mention 'summer.' Similarly, if it is August and it is sometime before the 25th of August, there is no need to mention the month - 'the 25th' is quite clear because of the time of the month you are speaking.
I am on summer vacation until the 25th of September!
When trying to explain that we are currently on vacation, we can use the actual date it ends or we can use an estimate.
"Actual" the real date your summer vacation ends
"Estimate" meaning an approximate time when your summer vacation ends
Examples:
"I am on summer vacation until the end of August!" (Estimate)
"I am on summer vacation until the 25th of September." (Actual)
休暇中であることを説明するときは、具体的な日にちとその終わりか想定される期間を使うことができます。
""Actual"" とは、具体的な夏休みの日にちと休暇の終了日です。
""Estimate"" とは、夏休みが終わると想定される日時を意味します。
例文
""I am on summer vacation until the end of August!"" (Estimate)
8月の終わりにまで夏休みです。（推定）
""I am on summer vacation until the 25th of September."" (Actual)"
9月25日まで夏休みです。（実際）
I am on summer vacation = you are on summer vacation right now
until + date = when your summer vacation ends
"I am on summer vacation until 20 September."
I am on summer vacation
今ちょうど夏休み中ということです。
until + date
いつ夏休みが終わるかです。
I am on summer vacation until 20 September.
夏休みは9月20日までです。
The verb 'am' is always used with the first person 'I' in grammar. It is usually followed by a present participle verb such as 'going'. You may say 'I am going on summer vacation until 31 December 2017'. In this case, you have not yet gone. But, if you have already started your summer vacation:
You may say:
I am on summer vacation until 31 December 2017
動詞の 'am'は必ず 'I' の後に使われます。現在分詞の'going'と一緒に使われたりします。'I am going on summer vacation until 31 December 2017'と言えます。 この場合はあなたはまで旅行に行っていませんが夏休みは始まっています:
このように使えます:
（英文）I am on summer vacation until 31 December 2017
（訳）私の夏休みは１２月31日 2017までです。
I am on summer vacation now and will only be going back to word/school on the "2nd January 2018"
>I am on summer vacation now and will only be going back to word/school on the "2nd January 2018"
Example 1
Him: You not in work?
You:I am on summer vacation now.
Him: Nice, how long?
You:going back to word on the "2nd January 2018"
Example 2
Him: Hi, you not at school?
You:I am on summer vacation now and will only be going back to school on the "2nd January 2018"
Other sentences
a. I am on summer vacation until .....
b. Summer vacation has started for me, going back to school/work on the ....
I am on summer vacation now and will only be going back to word/school on the "2nd January 2018"
(例文1)
Him: You not in work?
仕事中ですか？
You:I am on summer vacation now.
今、夏休み中です。
Him: Nice, how long?
いいですね。どれくらい（休暇）ですか？
You:going back to word on the ""2nd January 2018""
2018年1月の第2週に戻ってきます。
(例文2)
Him: Hi, you not at school?
学校は休みですか？
You:I am on summer vacation now and will only be going back to school on the ""2nd January 2018""
今、夏休みです。2018年の1月の第2週に学校が始まります。
他にも下記のように言うこともできます。
a. I am on summer vacation until .....
b. Summer vacation has started for me, going back to school/work on the ....
These expressions are very similar.
The only real difference is the word order and a slight grammar change.
They are both very simple and direct ways to express the fact that you're on vacation and
the duration of your vacation in only one sentence.
The first sentence is more formal than the second.
for the next (days) / until (date) - both of these are ways to indicate when an event will end
e.g. I'm going to the gym everyday for the next few days because I really need to lose weight for this wedding.
e.g. I'm going to the gym everyday of the week until the day of the wedding because I really need to lose this extra weight in time to walk down the aisle.
for the next (days) / until (date)-両方ともその出来事や行いが終わるまでを示すための表現。
例： ”I'm going to the gym everyday for the next few days because I really need to lose weight for this wedding.”
「この結婚式のための体重を減らさなくてはいけないので、私はこれから数日ジムに毎日通います。」
例；”I'm going to the gym everyday of the week until the day of the wedding because I really need to lose this extra weight in time to walk down the aisle. ”
「結婚式の日まで毎日ジムに行くつもりよ。だって、この余分な体重を結婚式の日までに減らさなきゃいけないから。」
My vacation begins on December 20th andends on December 2th.
When talking about vacation, there are many ways to tell someone the when your vacation begins or when it ends. Here are a couple suggestions:-
1. I won't be back to work until 1st January.
For most working people when vacation ends it's time to go back to work. In this case you can let someone know when you will be returning to work.
2. My vacation begins on December 20th andends on December 25th
This is a good wayto tell someone how long you will be on vacation and the dates.
休暇の期間を説明するなら、これはいろいろな言い方ができます。
例えば：
1. I won't be back to work until 1st January.（1月1日までは職場にいません）
ほとんどの人は休暇が終われば職場に戻ります。この文ではいつ職場に戻るかを伝えています。
2. My vacation begins on December 20th and ends on December 25th（休暇は12月20日から12月25日までです）
分かりやすい言い方です。休暇がいつからいつまでなのかを説明しています。
I am on summer vacation until the first of September
I am on vacation and won't be back until the first of September
These two sentences should help you to explain yourself in front of your friends or co-workers. For example - I will be on summer vacation and won't be able to do anything until July.
二通りの言い方をご紹介しました。このように言えば、同僚や友達に状況を説明できると思います。
例：
I will be on summer vacation and won't be able to do anything until July.（7月までは夏休みなので何もできません）
I'm on summer vacation.
I'm on summer break.
上記のように英語で表現することができます。
summer vacation は「下記休暇」のようなニュアンスです。
summer break も近いニュアンスで、「夏休み」と訳せます。
例：
Where did you go for your summer vacation?
下記休暇はどこへ行きましたか？
お役に立てれば嬉しいです。
日本 
イギリス 
南アフリカ 
アメリカ合衆国 
カナダ 
