The onsen is only closed one day a month, and that's the day I went!
If the onsen is closed the one day you went, that is a disappointing experience. You want to share how sad you are that you weren't able to go by saying something like "The onsen is only closed one day a month, and that's the day I went!". Using this is dramatic and gets the point across that it was bad luck that was the day you choose to go.
あなたが温泉に行った日が閉館日だったなら、とっても残念ですよね。どれほど悲しかったかを、"The onsen is only closed one day a month, and that's the day I went!"（ちょうど温泉に行った日が、月に1回の閉館日だった！）ということで伝わるでしょう。こう言うと、自分が選んでいった日が運の悪いことになってしまったということが伝わります。
I went to the hot spring the other day but it was their monthly fixed holiday.
I went to the Onsen yesterday and it was the one day a month they close.
「定休日」」は fixed holiday や store/shop holiday、または「毎週水曜定休」なら close every Wednesday などと言えます。
1) I went to the hot spring the other day but it was their monthly fixed holiday.
「この前温泉に行ったら、月1の定休日だった。」
このように monthly fixed holiday が使えると思います。
2) I went to the Onsen yesterday and it was the one day a month they close.
「昨日温泉に行ったんだけど、月１の休みの日だった。」
It was the one day a month they close. のように文で「月一の定休日」を説明した言い方。
ご参考になれば幸いです！
The hot spring closes once a month and that is the day I decided to go, just my bad luck!
I am very unlucky, the hot spring was closed, it was their monthly off day!
The hot spring has a one-day monthly closure on the day I was there!
"The hot spring closes once a month and that is the day I decided to go, just my bad luck!"
"once a month" means one day every month
"I am very unfortunate, the hot spring was closed, it was their monthly off day!"
"unfortunate" meaning that you were unlucky
"The hot spring has a one-day monthly closure on the day I was there!"
"monthly" this means once a month every month
"The hot spring closes once a month and that is the day I decided to go, just my bad luck!"
（その温泉は月に一回休業日があって、私が行った日がちょうどその日でした。運が悪かったです）
"once a month" は「月に一回」という意味です。
"I am very unfortunate, the hot spring was closed, it was their monthly off day!"
（すごく運が悪いです。温泉が閉まっていました。月一回の休業日だったんです）
"unfortunate" は「運が悪かった」という意味です。
"The hot spring has a one-day monthly closure on the day I was there!"（その温泉は月に一回休業日があって、私が行った日がちょうどその日でした）
"monthly" は「月に一回」という意味です。
I went to the hot spring; however they were closed as it was a bank holiday.
I found that the spring was closed on the public holiday.
1. Saying that it was a bank holiday shows that it is a time where some people would not be working this is the same as a public holiday. Some shops and office workers would not be working on these days.
Just my luck - I went to an onsen spring and it was the one day in the month when it was closed!
If you go to an onsen hot spring, but it is closed, and it is the one day that they are closed every month, then you may express your feelings by using the abovementioned example.
Just my luck! - a sarcastic expression which means you had extraordinarily bad luck in a specific situation.
温泉に行ったけどそれがたまたま月に一回の定休日で閉まっていたということなら、上記の文を使ってその気持ちを表現できます。
Just my luck!（運が悪いな）
- ついてないことがあったことを伝える皮肉。
I went to the hot spring but unfortunately it was on the day of the month they close.
When I went to the hot spring it was closed! They close one day a month.
We use 'unfortunately' to express that something is sad, disappointing,. And you can add the information that the hot spring closes one day a month.
-I went to the hot spring but unfortunately it was on the day of the month they close.
-When I went to the hot spring it was closed! They close one day a month.
unfortunately' は悲しい気持ちや残念な気持ちを表します。ここに「温泉に月に一回の定休日がある」という情報を加えます。
-I went to the hot spring but unfortunately it was on the day of the month they close.
（温泉に行ったけど、不運なことに月に一回の定休日でした）
-When I went to the hot spring it was closed! They close one day a month.
（温泉に行ったら閉まっていました！月に一回定休日があるんです）
The hot spring closes one day every month and i picked that day to go!
I picked the one day a month the hot spring closes to visit!
When saying that something closes for a day once a month you can say 'closes one day a month' or 'one day a month the hot spring closes'
I picked means you chose to do something (that day to go to the hot spring)
月に一回定休日があることは、
'closes one day a month'（月に一回定休日がある）
や、
'one day a month the hot spring closes'（その温泉の月に一回の定休日）
で表すことができます。
'I picked' は「選んだ」という意味です。ここでは「温泉の月に一回の定休日を選んでしまった」と言っています。
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