Amazon has a new plan to win goodwill with Amazon Prime customers: Massive, one-day discounts. On Wednesday, July 15, Amazon is holding Amazon Prime Day to celebrate the ecommerce site’s 20th anniversary.

According to the company, Prime Day will include thousands of “Lightning Deals” along with seven special sales in the United States and other major international markets. The company says it will offer more sales on July 15 than it did on Black Friday.

Although the event is planned around Amazon’s 20th anniversary, the discounts will only be available to Prime members, who pay $99 a year for unlimited, free two-day shipping. Amazon Prime’s success relies upon getting customers to order the everyday essentials they would normally buy in person from small local stores, supermarkets, or big-box retailers.

There’s another reason Amazon is holding this mid-summer sale: It is facing a new wave of competition. Walmart is expected to launch an Amazon Prime rival this summer, and eBay is set to launch a similar subscription service as well.

Amazon may have gotten the idea for Prime Day from one of its biggest global rivals. Ecommerce giant Alibaba created its own sales holiday, called Singles Day, and the initiative generated a staggering $9 billion in sales for the Chinese company.