noun
customer appreciation day
A retail sales event where stores offer discounts or special services to thank customers. Often held on a fixed day, such as the 20th of each month, by supermarkets and other shops.
毎月20日はお客様感謝デーで、食料品が5%引きになります。
The 20th of every month is Customer Appreciation Day, and groceries are 5% off.
お客様感謝デーのチラシが入っていた。
A flyer for the Customer Appreciation Day was in the newspaper.
A compound of お客様 (customer, with honorific prefix and suffix) + 感謝 (gratitude) + デー (day, from English). A modern retail term.