We call all the days except the weekend a week day. If a product can only be purchased or is only available on a weekday. You cannot get it on Saturday or Sunday. Working days only, which are the usual 9-5 office hours.
"We have a weekday special"
週末以外の全ての日を week day と呼びます。もしある商品が only available on a weekday（平日しか買えない）のであれば、Saturday（土曜日）や Sunday（日曜日）に手に入れることはできません。Working days（平日）のみで、基本の営業時間は9時から5時です。
例：
"We have a weekday special"
「平日限定の価格があります」
Another way to say that something is available (for purchase) is to say that "you can only buy it."
A. I really like this beer, but it's so hard to get.
B. Why's that?
A. Well, to start you can only buy it on the weekend, Friday through Monday, and I work on the weekends. Also, there aren't a lot of stores close to me that sell it.
availableのわかりに"you can only buy it."と言えます。
（英文）
A. I really like this beer, but it's so hard to get.
B. Why's that?
A. Well, to start you can only buy it on the weekend, Friday through Monday, and I work on the weekends. Also, there aren't a lot of stores close to me that sell it.
(訳）
A:私はこのビールがとても好きです。手に入れるのが難しいのです。
B:なぜですか？
A：週末にしか買えないのです。金曜日から月曜日と週末に私は働いています。また近くにこれを販売しているお店がないのです。
You may only purchase this product between Friday and Monday
You would like to buy a large sack of potatoes you have seen advertised in your local supermarket. You go down to the supermarket with your car and ask the shop assistant about the potatoes.
A: "Excuse me, but where are the large sacks of potatoes?"
B: "We have those out the back of the shop, but you may only purchase this product between Friday and Monday."
A: "That's crazy! Why?"
B: "We don't have anyone here to help with the bags on the other days. Sorry!"
地元のスーパーの広告で見た大きな袋に入ったじゃがいもを買いたいと思っています。
車でスーパーに行き、店員にじゃがいもについて尋ねます。
例文
A: "Excuse me, but where are the large sacks of potatoes?"
すみませんが、大きな袋に入ったじゃがいもはどこですか？
B: "We have those out the back of the shop, but you may only purchase this product
between Friday and Monday."
店の奥にありますが、金曜日から月曜日までしか購入できません。
A: "That's crazy! Why?"
そんな。どうしてですか？
B: "We don't have anyone here to help with the bags on the other days. Sorry!"
他の日には、袋をここまで運ぶ人がいないんです。すみません。
The product can only be purchased from Friday to Monday.
*The product can only be purchased from Friday to Monday.
This means that people can buy the product only on these 4 days.
For example;
A: When is X available for purchase?
B: The product can only be purchased from Friday to Monday.
例文
A: When is X available for purchase?
（Xはいつ買えますか？）
B: The product can only be purchased from Friday to Monday.
（その商品は金曜日から月曜日の間だけお買い上げ頂けます。）
ポップ用なら ”available only from Friday through Monday" と短く書いても良いかも知れません。
＊Available ＝利用出来る／入手できる
"Only available from Friday to Monday." This explains that they can only buy the product between Friday and Monday.
"Purchasable only from Friday to Monday." This is another way of explaining that the product is only available from Friday to Monday.
"Only available from Friday to Monday." という例文について
この文は、金曜日から月曜日の間だけしか商品を買うことができないということを説明します。
"Purchasable only from Friday to Monday." という例文について
この文は、上記と同じ意味ですが、別の言い方です。
The purchase of this product is restricted to Friday/Saturday/Sunday & Monday only!
Some products may be difficult to man-handle/manage/carry etc
And /or special skills may be needed to service these products:
In that case then sales would be described as " Restricted":-D
"The purchase of this product is restricted to Friday/Saturday/Sunday & Monday only!"
持ち運んだり、管理したり、人の手で動かすのが難しい製品もあるかもしれません。
または（それに加えて）、特別なスキルがないと提供できないのかもしれませんね。
そのような場合、販売が「Restricted（限られた）」と表せるでしょう。
"The purchase of this product is restricted to Friday/Saturday/Sunday & Monday only!"
〔訳〕この製品は、金、土、日、月曜日のみ購入可能です。
This special offer is only available from Friday-Sunday.
This is only valid from Monday - Friday.
This special offer is only valid from Monday - Friday. - This means that the special offer does not apply on Saturdays and Sundays.
It is common that you can only purchase certain things on certain days. If it is a product that has been reduced, it is usually a plan to get customers into the shop on days that are not so busy.
Example:
Q: Excuse me, is the roast chicken still on offer?
A: Sorry madam, that offer only applies from Monday-Friday.
This special offer is only valid from Monday - Friday.
（この特価は月曜から金曜まで限定です）
- 土曜、日曜は特別価格でないことを表します。
ある物が特定の曜日にしか買えないということはよくあります。お客さんの少ない日に人を呼び込むための作戦のことが多いです。
例:
Q: Excuse me, is the roast chicken still on offer?（ローストチキンはまだありますか）
A: Sorry madam, that offer only applies from Monday-Friday.（申し訳ありません、あれは月曜から金曜限定なんです。）
販促用のポップのため、タイトルのような表現にしてこのようにできます：
Limited Friday to Monday
limitedは「限定されている」という意味です。
Limited from Friday to Mondayも使えますが、fromを省略すればシンプルなタイトルにできます。
Friday to Monday Only
こちらで「だけ」のonly を使ってます。
From Friday to Monday Onlyのfromも省略しました。
Only available Friday to Monday
この表現は「（販売）可能の」意味のavailableを使っています。
またfromも略しました。
イギリス 
アメリカ合衆国 
南アフリカ 
アイルランド 
