The hot spring is open until 12pm and from 5am to 10am.
It is open until 12pm this evening and from 5 tomorrow morning to 10.
The hot spring is open until 12 tonight and from 5 in the morning until 10.
You can refer to the hot spring as 'the hot spring' but if the person already knows what you are talking about, you can just refer to the hot spring as 'it'.
To talk about the time you can use the terms '12pm', '12 tonight', `12 this evening', 'midnight'. For 5am you can use '5am', '5 in the morning', '5 tomorrow morning'. For 10am you can use '10am' '10 in the morning' '10 tomorrow morning', or in this context the person may already know that you mean 10am, so you might be able to just say '10'. They may then clarify this by asking '10am' and you would reply 'yes'.
You use the word 'until' to show that this is the final or last time, and the word 'from' to show that this is when it starts.
温泉のことは 'the hot spring' と言えます。ただ、それについて話していることが既に相手に伝わっているなら、単に 'it' で表せます。
深夜0時は、'12pm' や '12 tonight' '12 this evening' あるいは 'midnight' と言えます。
午前5時は、'5am' '5 in the morning' または '5 tomorrow morning' と言えます。
午前10時は '10am' '10 in the morning' '10 tomorrow morning' になりますが、ここでは文脈から「午前」のことだと分かるでしょうから、単に '10' でもいいかもしれません。もしかしたら、この後相手は '10am' のことかと確認してくるかもしれません。そうしたら、'Yes' と答えましょう。
'until' は、それが終わりの時間であることを表します。そして、'from' はそれが始まりの時間であることを表します。
The hot spring is available to use between 5am and 10am and from ___to 12 midnight.
Before my explanation, I'd like to point out that there seems to be a missing time here. If you would like to tell guests that there are 2 time periods, then they both should be made clear. After the 5-10 morning shift, when does the next time frame start?
There are various ways we can talk about time periods. We can use the "from to" format, the "between and"and the "from until" formats. All of these formats tell people that these are the times the service is available, and that any time before or after these times, the service is unavailable. So in your case, the hot springs are open from 5am to 10am, between 5am and 10am, or from 5am until 10am. However, there does need to be an additional time added to clear up the "closes at 12 midnight" section of this answer.
説明の前に、ここでは一つ時間が抜けているように思います。お客さんに二つの期間について伝えたいなら、それらはどちらも明確にすべきです。朝の5時から10時までの後、その次は何時から0時までなのですか？
期間の表し方はいろいろあります。例えば、"from to" の形式、"between and" の形式、そして "from until" の形式もあります。これらの形は全て、そのサービスが利用可能な時間を表します。
ですからあなたの場合は、
'The hot springs are open from 5am to 10am/between 5am and 10am/from 5am until 10am.'（温泉は午前5時から午前10時まで開いている）
となります。
ただし、この場合、ここにもう一つ「0時に閉まる」という情報を加える必要があります。
Operating times for the hot spring is from 5 am to 10 am and it closes at midnight!
The hot spring closes at 12 am and it is open from 5 am until 10 am!
Operating times for the hot spring is from 5 am to 10 am and it closes at midnight!
"Operating time"
the time that a place or an establishment (eg: a hotel, hot spring, or store) is open
The hot spring closes at 12 am and it is open from 5 am until 10 am!
"close"
indicating that you stop working
Operating times for the hot spring is from 5 am to 10 am and it closes at midnight!（温泉は朝は5時から10時まで、夜は12時まで利用できます）
"Operating time"
ホテル・温泉・お店などの施設が開いている時間。
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The hot spring closes at 12 am and it is open from 5 am until 10 am!（温泉は夜は12時まで、朝は5時から10時まで利用できます）
"close"
お店が営業を終えること。
The hot spring is open between 5am - 10am, till midnight
Using the term 'am' makes it clear that you are referring to the morning.
also 'midnight' adds specificity to which 12 and avoids confusion with 12 midday.
The onsen is available between the hours of 5:00AM-12:00AM
OPEN 5:00AM CLOSED 12:00AM
Onsen Hours: 5:00AM - 12:00AM
There are many ways to post a formal open to close signage. Here are a few examples.
-The onsen is available between the hours of 5:00AM-12:00AM
-OPEN 5:00AM CLOSED 12:00AM
-Onsen Hours: 5:00AM - 12:00AM
営業時間を看板で伝える場合、これはいろいろな書き方ができます。
例えば：
-The onsen is available between the hours of 5:00AM-12:00AM（温泉は午前5時から午前12時までご利用できます）
-OPEN 5:00AM CLOSED 12:00AM（オープン：午前5時 クローズド：午前12時）
-Onsen Hours: 5:00AM - 12:00AM（営業時間：午前5時 - 午前12時）
The onsen is open until 12 at night and from 5 to 10 in the morning.
If you work at a Japanese hotel and want to explain to customers the hours of the onsen (hot spring) are that it is open until 12 at night and from 5 to 10 in the morning, then you may use the above exampled statement.
日本 
イギリス 
アメリカ合衆国 
南アフリカ 
