Amazon Prime Day, a made-up holiday that's become bigger than Black Friday, is coming soon. Here's why it's such a big deal.

Getty/Rick T. Wilking

July is typically a slow month for retailers - until Amazon came up with Prime Day.

• Prime Day is Amazon's made-up holiday, when it boasts heavy discounts that it says rival Black Friday. The deals are available exclusively to Amazon Prime members.
• This year's date has not yet been officially announced, but Amazon may have leaked the date inadvertently earlier this month.
• The deals are not advertised ahead of time, but expect heavy discounting on Amazon devices and top sellers like the Instant Pot, as well as a coupon for book purchases.

Amazon Prime Day is almost here.

Amazon's made-up holiday, when it boasts Black Friday-like discounts exclusively for Prime members, is always held during the second week of July.

And according to an apparent leak, it will likely be July 16 this year. Last week, the company posted a banner to its UK website indicating that July 16 would be the date of the event, TechRadar reports.

If the apparent leak is to be believed, the deals will go on for 36 hours and kick off at noon that day.

That would make it six hours longer than 2017's Prime Day, which itself was six hours longer than the year prior.

In response to the leak, an Amazon spokesman told Business Insider: "We announced last year that Prime Day would return; we don't have additional details to share yet."

Before the leak, July 10 was the rumored date for Prime Day. That is the same day it kicked off in 2017.

Expect sales on items like Amazon devices, gift cards, and popular items like TVs and the Instant Pot, as well as a coupon for book purchases. Last year, the Echo Dot was the most-sold item worldwide, and the Instant Pot was the most-sold item in the US.

Prime Day is now in its fourth year - it started in 2015 - but it's grown quickly. It's now one of the biggest sales days on Amazon's calendar, rivaling only Black Friday in importance.

In 2017, Amazon said Prime Day led to "more new Prime members joining Prime than any single day in Amazon history." It was also the largest single sales day in the company's history, eclipsing Black Friday in 2016. It would later itself be eclipsed by 2017's Cyber Monday, which remains Amazon's biggest sales day in history.

As Prime Day grows larger, its importance grows as well. Prime is increasingly important to Amazon, as members tend to be more loyal to the website and shop there before they go anywhere else. They also tend to purchase more items and more frequently.

Amazon also keeps adding new services and perks, like Prime Day, to keep members happy in the ecosystem.

"Prime delivers such massive scale and features that we believe it would be very difficult for any company to replicate and compete against, and Amazon continues to expand and add more value to Prime by adding new benefits and growing existing offerings," JP Morgan analysts wrote, arguing that Prime is actually worth $785 a year.