とてもニューヨークで楽しまれたことが伝わる英語は「The one month I spent in New York just flew by!」。
他のアンカーも言っているように、楽しんでいると時間の経過を早く感じるため「Time flies」と言います。この場合は過去形なので、「flew by」にしました。
また、「Just」を入れることで、強調しています。
その強調で、充実感のニュアンスをキャッチしています。
My month in New York was great, but the time flew by.
The month I spent in New York went by so fast.
The month I had in New York went by so quickly.
All of these answers explain to someone that your trip to New York went by quickly even though you were there for a whole month.
There is a common saying in the UK which is 'Time flies when you're having fun.' This can be applied to the answers above. Usually time seems to move more slowly when we are not enjoying something.
When something 'fly's by' it means that it went very quickly.
三例とも、1カ月間ニューヨークにいたけどあっという間だったということを伝える言い方です。
イギリスでよく使われることわざに、'Time flies when you're having fun.'（楽しい時間は過ぎるのが速い）というのがあります。これも当てはまると思います。大抵楽しんでいない時は、時間がたつのが遅く感じますね。
'fly by' は、何かがすぐに去ってしまったことを表します。
The month spent in New York passed in a blink of an eye.
taichiさん
ご質問どうもありがとうございます。
下記の言い方ではいかがでしょうか。
The month spent in New York passed in a blink of an eye.
--- in a blink of an eye = あっという間
ご参考にしていただければ幸いです。
To explain that your time in New York went by quickly, then you can explain it in certain ways:
-The month I spent in New Your went by very fast
-The month I spent in New York flew by so quickly
-Time flies when you're having fun. My time in New York went by quickly
ニューヨークでの時間があっという間だったと言う場合、このように表せます：
-The month I spent in New Your went by very fast
（ニューヨークで過ごした一か月はあっという間だった）
-The month I spent in New York flew by so quickly
（ニューヨークで過ごした一か月はあっという間だった）
-Time flies when you're having fun. My time in New York went by quickly
（楽しい時間は過ぎるのが速い。ニューヨークでの時間はあっという間だった）
Common in conversation is to mention how quickly time can pass when you are busy or enjoying it. The most common is "time flies when you are having fun". If you want to say how quickly your month went by you could say "my month in New York went by so quickly" or "one month in New York passed by so quickly". Lastly, you could express yourself by saying "my days were so busy that they just flew by".
会話では「忙しいと時間があっという間」とか「楽しい時間はあっという間」のような話がよく出ます。
最も一般的なのは "Time flies when you are having fun".（楽しい時間はあっという間）です。
「一カ月があっという間だった」は次のように言えます。
"my month in New York went by so quickly"
"one month in New York passed by so quickly"
（ニューヨークでの一カ月はあっという間でした）
最後に、"my days were so busy that they just flew by".（毎日忙しくてあっという間でした）という言い方もできます。
"One month in NY flew by" - the expression "flew by" means that time went very quickly.
"One month in NY was too short" - the expression "was too short" means that time went by fast and you wish you had more time.
"The month I spent in NY went by so quickly" - the expression "went by so quickly" means that the time went very fast.
All of these expressions give the idea that the time went by quicker than you expected.
"One month in NY flew by"（ニューヨークでの一カ月はあっという間だった）
→"flew by" は「時間があっという間に過ぎた」という意味です。
"One month in NY was too short"（ニューヨークでの一カ月はあっという間だった）
→"was too short" は「あっという間だったのでもう少し長くいたかった」という意味合いです。
"The month I spent in NY went by so quickly"（ニューヨークで過ごした一カ月はあっという間だった）
→"went by so quickly" は「時間があっという間に過ぎた」という意味です。
これらの表現は全て、時間があっという間に過ぎたことを伝えます。
I know it sounds crazy, but it felt like I barely arrived in NY and then it was time to go back home.
I was in NY for a couple of weeks and before I knew it, it was time to return home.
Time flies when you're having a good time!
I know it sounds crazy, but it felt like I barely arrived in NY
and then it was time to go back home.
This implies that the person had such a great time in NY that
the time flew by unbelievably fast.
I was in NY for a couple of weeks and before I knew it, it was
time to return home.
Before I knew it means that the stay in NY was such a fantastic
experience that it ended much too soon.
Time flies when you're having a good time!
This means that when you're having fun, time seems to move
more quickly.
I know it sounds crazy, but it felt like I barely arrived in NY and then it was time to go back home.（おかしいですけど、ニューヨークに着いたと思った次の日には帰国の便に乗っていたみたいな感じでした）
→これは「ニューヨークでの時間はすごく楽しくてあっという間だった」というニュアンスです。
I was in NY for a couple of weeks and before I knew it, it was time to return home.（ニューヨークに2、3週間いて、気付いたら帰国の日になっていました）
→"Before I knew it"（知らぬ間に）は、ニューヨークでの時間がすごく楽しくてあっという間だったことを表します。
Time flies when you're having a good time!
→これは「楽しい時間はあっという間に過ぎていく」という意味です。
イギリス 
ドイツ 
南アフリカ 
オーストラリア 
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