My birthday is next month, so it would be nice if I could see you then.
I really wanted to see you on my birthday.
I'd love to see you on my birthday.
When you use the phrase "it would be nice..." you are implying a want or a wish. For example:
- It would be nice if I could see you on my birthday.
- It would be nice if you could take out the trash.
- It would be nice if you could do the dishes every now and then.
**It is very easy to sound whiny/condescending when you use this phrase. Be careful.**
I always say that it is better to be direct with your significant other, especially in this situation and it's your birthday! You could just tell them:
- I really wanted to see you on my birthday.
- I really wanted you to make time for me on my birthday.
- I really don't want anything else but to see you on my birthday.
Again, direct and to the point:
- I'd love to see you on my birthday.
- I'd really like to see you on my birthday.
- I'd love it if you could come see me on my birthday.
"it would be nice..." （だったらいいのに）というフレーズを使う時は希望を意味しています。たとえば:
- It would be nice if I could see you on my birthday.（私の誕生日にあなたに会えたらいいな）
- It would be nice if you could take out the trash.（あなたがごみを出してくれたらいいな）
- It would be nice if you could do the dishes every now and then.（たまにはあなたがお皿を洗ってくれたらいいな）
**不平不満を言っているあるいは恩着せがましく聞こえやすいので、このフレーズを使う時には気を付けてください**
大切な人に直接伝える方が良いと思います。特にこの状況ではあなたの誕生日ですので、以下ように言うとよいでしょう：
- I really wanted to see you on my birthday.（私の誕生日にはあなたにぜひ会いたい）
- I really wanted you to make time for me on my birthday.（私の誕生日にはぜひあなたに時間をつくってほしい）
- I really don't want anything else but to see you on my birthday.（私の誕生日には何もほしくないけどぜひあなたに会いたい）
3. We can have our own private birthday party another day, don't worry!
1. this phrase means that you will miss this person.
2. It's such a shame that.... This phrase means that 'it's a little sad that..'
3. Our own private party = You can celebrate your birthday later together.
1.この句は、あなたがこの人がいなくて寂しいということを表す表現です。
2.'it's a little sad that..' このフレーズは、「...は少し悲しいです。」という表現です。
3.Our own private party =後日誕生日を一緒に祝おうね、という表現です。
My birthday is next month so I wish I could see you then!
「来月が誕生日」は、My birthday is next monthとなります。「会えないけど会えたらいいのに」というように、「現実的には叶わないけどそうだったらいいのに」という気持ちを表したいときは、wishを使うといいです。（学校で習った「仮定法過去」という使い方ですね）「会えたらいいのに」という現在の状況を話す場合は、wish＋過去形の形で文を作ります。
その他の例：
I wish I could go to New Zealand! ニュージーランドに行けたらいいのに！（現実には無理だけど）
I wish I could go to the concert! コンサートに行けたらいいのに！（現実には無理だけど）
ちなみに、もし現実的に会えるかどうかわからない状況のときは、My birthday is next month so I hope I can see you!（来月私の誕生日だから会えたらいいな！） / My birthday is next month so it will be awesome if I can see you!（来月私の誕生日だから会えたら最高だな！）という表現もあります。
誕生日であることをアピールして、相手の方が予定を変えて会ってくれるといいですね！わたしもそう願っています＾＾
It would have been great to see you on my birthday next month.
It's my birthday next month,I'd have loved to see you.
"It would have been great to see you on my birthday next month."and "It's my birthday next month,I'd have loved to see you."are appropriate to express regret and sadness .
You could also say:
-I feel so sad about you not being able to come on my birthday
- "It would have been great to see you on my birthday next month."
「来月の私の誕生日に会えたらよかったんだけどな」
- "It's my birthday next month,I'd have loved to see you."
「来月は私の誕生日だから、あなたに会えたらよかったんだけどな」
両方とも、残念な気持ちと悲しみを表す適切な文章です。
他には、以下と言ってもOKです。
- "I feel so sad about you not being able to come on my birthday"
「私の誕生日にあなたが来れなくて悲しいわ。」
You would want your partner to be with you on your birthday so if they are busy you might say 'i would really like to see you on my birthday' or 'it would be nice to see you on my birthday' this would tell them that you would like to be/spend time with them
誕生日にはパートナーと一緒に過ごしたいですよね。ですから、もし相手が忙しいなら、次のように言えます。
'I would really like to see you on my birthday'（誕生日にはあなたに会いたいです）
または、
'It would be nice to see you on my birthday'（誕生日にはあなたに会いたいです）
これで、相手と一緒に過ごしたいことが伝わります。
"My birthday is next month, so it would be nice if I could see you on that day"
"As it is my birthday, I would have liked to spend time with you"
In order to explain to your siginificant other that you would like to have of spent time with them on your birthday, you can state "As it is my birthday, I would have liked to spend time with you". This sentence explains that you were upset that you could not see them as it was an important day to you.
大切な人に誕生日に一緒に過ごしたかったと伝えたいなら、次のように言えます。
"As it is my birthday, I would have liked to spend time with you"（誕生日だから、一緒に過ごしたかった）
この文は、大切な日に相手に会うことができず不満だったことを表します。
I just thought it would have been nice to see you on my birthday.
★ポイント：来月会えない/会いたかったなー/軽く
現時点で、来月会えないことが分かっているので、it would have been nice と過去のことにするのがよいですね。根に持ってではなく（笑）「軽く」伝えたいので、I just thought と「ちょっとこう思ったんだよね～」としてみました。
I just thought it would have been nice to see you on my birthday.
英語職人
アメリカ合衆国 
イギリス 
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