Amazon Prime Day permanently altered the retail calendar — I charted its history over 11 years to explain exactly how

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Amazon Prime Day continues to shake the core of the retail industry and shape the shopping calendar by getting bigger and longer each year. Kara Birnbaum / NBC NewsYou’ve definitely heard of Amazon Prime Day even if you’ve never bought something during the event. It’s nearly impossible to avoid: Leading up to the Prime member-exclusive sale, there are commercials about it on YouTube, influencers posting about it on social media, flashy billboards advertising it in Times Square and media outlets (like NBC Selected) telling you everything you need to know about it. At this point, Prime Day is fully embedded in consumer culture — that’s especially impressive considering it’s only been around for about a decade, and it’s not tied to the winter holiday shopping season like Black Friday and Cyber Monday are.

Ever since its inception, Amazon has scaled Prime Day to record-breaking heights. The event generates billions of dollars in global sales and drives up e-commerce activity across retailers. This year, Prime Day made already made history as Amazon’s most profitable sale ever, even though the retailer made major changes to its format. And with Prime Big Deal Days, a.k.a. October Prime Day, coming up on Oct. 6, the retailer has another chance to impress shoppers with discounts and blow performance expectations out of the water.

To contextualize Prime Day and its impact on e-commerce, I charted its history over the past 11 years. I also consulted experts about its growth, what it signals about consumer behavior and whether deals are actually worth buying.

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The first-ever Prime Day took place on July 15, 2015 to celebrate the company’s 20th anniversary, according to Amazon. It lasted 24 hours and was available to members in nine countries. Since 2015, Prime Day has expanded its reach — Amazon now hosts the sale for four days in over 20 countries, and it runs a second version of Prime Day, Prime Big Deal Days, in October to kick off the holiday shopping season.

One of the factors that makes Prime Day so unique is that it’s an event Amazon manufactured, unlike Black Friday and Cyber Monday, which are tied to the holiday shopping season. Prime Day (the first one, anyway) is traditionally held between the end of June and mid-July, which is a strategic decision on the company’s part: The summer is a slow period for retailers, and Prime Day is an attempt to remedy that.

“Prime Day provides Amazon with a jolt during an otherwise dormant shopping season,” says Dr. Ross Steinman, a professor of consumer psychology at Widener University. Hosting Prime Day during the week is a strategic decision, too: Summer weekends are reserved for relaxing, sleeping in, leisure activities and traveling, but Amazon knows it can capture shoppers’ attention during the week when they’re using their phones and computers more.

There’s three big reasons why Amazon hosts Prime Day: to attract new Prime members, retain the members it already has and drive sales to its marketplace.

Amazon’s goal is to accrue an army of repeat shoppers who take advantage of everything a Prime membership offers them year-round, not just during one big sale. Prime Day acts as an entry point for new Prime membership sign-ups, and a way to remind existing members why the loyalty program is worth $139 a year (up from its original $99 price at inception).

The sale puts Prime’s benefits on full display and exposes shoppers to the retailer’s “ecosystem of consumption,” meaning its network of platforms like Prime Music, Whole Foods grocery delivery, Prime Video, Audible and Kindle Unlimited. And once you’re in Amazon’s ecosystem, it’s hard to leave, says Steinman.

“Amazon’s goal is to be sticky,” he says. “Consumers in the Amazon ecosystem are going to spend largely double what non-Prime members will.”

As for driving sales to Amazon’s marketplace, hundreds of brands offer deals during Prime Day, but those the retailer owns, like Fire, Kindle, Ring and Blink, tend to drop prices the most. Discounting Amazon-owned devices is particularly lucrative for the retailer because they’re designed to increase your purchases on Amazon, says Steinman. The majority of this tech is equipped with Amazon Alexa, a virtual assistant who can notify you about deals and make purchases if you give her permission.

There’s one more reason Prime Day is such an important event for the company: “It’s a stress test for the holidays,” says Steinman. “Prime Day creates an artificial surge in orders, similar to what the retailer experiences between November and December, so it provides Amazon with an opportunity to do a test run. They can see if they need to work out any kinks as they get closer to the formal holiday shopping season.”

Amazon Prime Day started as a 24-hour event in 2015, and it gradually extended in length before becoming known as a 48-hour event between 2019 and 2024. Then, in 2025, Amazon doubled Prime Day to four days, which seems to be the new norm, at least for now — 2026 was the second year with this timeframe.

Experts agree that making Prime Day four days long was a wise move on the retailer’s part, but there’s more to it than assuming more time to shop equals more purchases — it’s also about optics. “When you expand into a four-day event, you’re really putting an anchor down and saying, ‘this is a Black Friday shopping type moment,’ signaling to consumers that’s what they should expect,” says Vivek Pandya, the manager of Adobe Digital Insights.

Extending Prime Day aligns with shoppers’ general awareness around the sale, too. Hosting it under a tight time constraint built hype, which worked well to draw consumers in during the early years. But now, Prime Day is permanently embedded in the retail calendar, so Amazon doesn’t need to build the same type of excitement around it. Instead, the retailer may as well give shoppers the opportunity to make multiple transactions, says Pandya.

Finally, a four-day sale acknowledges that consumers are adopting more advanced budget management strategies as they’re concerned about the current volatile economic environment, says Steinman. They’re deliberately looking for deals using browser extensions to track prices, for example, because they want to find real value — a longer timeframe to shop lets them do so.

Over a decade in, shoppers thought they knew what to expect from Prime Day. But for the second year in a row, Amazon threw them a curveball: It hosted the 2026 sale in June rather than July, and repeated the four-day format.

Scheduling Prime Day for June isn’t unheard of — prior to 2026, Amazon did it once in 2021. But after years of building a habit among Prime members and teaching them to plan for major deals in July, it was a potentially risky move, says Melissa Murphy, an adjunct professor at Carnegie Mellon University’s Tepper School of Business. So why did the retailer do it?

I spoke to Jamil Ghani, the vice president of Worldwide Amazon Prime, who says Amazon thinks deliberately about the ideal timing for its mega sale every year. Because June and early July 2026 was packed with events like Father’s Day, the United States’ 250th anniversary on July Fourth and the World Cup, hosting the sale beforehand made sense — the June date let shoppers prepare for each event by saving on related products. Ghani says Amazon got positive feedback from its loyalty members about 2025’s four-day timeframe, so the retailer kept it for 2026. Shoppers liked the additional time to discover new brands, find the best deals from their favorites, curate their shopping cart and check out when they were ready, rather than in a rush. Amazon hasn’t disclosed whether it’s keeping the June date or four day format for Prime Day 2027, or even said if the event is happening — but we can almost guarantee that it will.

Even with the date change, Prime Day 2026 saw high year-over-year growth. Amazon doesn’t disclose sales figures, but Adobe estimates that U.S. retailers drove $26.4 billion in online spending from June 23 to June 26, the period during which Prime Day took place — this represents 9.3 percent growth year-over-year, beating Adobe’s initial forecast. These figures cement Prime Day’s identity as the summer sale, and show how much other retailers embraced hosting corresponding, competing savings events, albeit earlier than usual. It’s undeniable that Amazon has achieved its goal of making shopping activity flourish during an otherwise sleepy retail season.

As counterintuitive as it sounds, a lot of this growth is in part due to consumers’ economic concerns around inflation and the rising cost of living. “During most of the year, consumers are pulling back on non-essential spending to manage high costs, but once retailers present them with deals that they see strong value in, they’ve been over-indexing on spending,” says Pandya.

Based on the number of units purchases, bestselling items from Prime Day 2026 include Premier Protein Shakes, Liquid IV electrolyte powder, Temptations Cat Treats, Dawn Powerwash Dish Soap Spray and Hefty Ultra Strong Trash Bags, according to Numerator. These items are all personal purchases you need to frequently restock, which tells experts that people are mostly shopping for themselves during Prime Day. The event is during the summer, so members buy items they need, unlike Black Friday and Cyber Monday, which people use to buy items they want, as well as holiday gifts.

Premier Protein Shake (12-Pack)$26.70

Dawn Powerwash Spray Dish Soap Starter Kit$17.50

Liquid I.V. Hydration Multiplier$23.30

Hefty Ultra Strong Trash Bags$18.38

There’s an inaccurate stereotype about shoppers during huge sale events like Prime Day, says Steinman. “The perception is that somebody’s going to get swept up in excitement and engage in a number of impulse purchases,” he says. “But by and large, that’s not what happens on Prime Day.”

For the most part, Prime Day shoppers are savvy — they’re conscious about using the sale to their advantage and spending strategically, says Steinman. Many compare prices across retailers to determine whether a deal is worth taking advantage of, and save their “bucket list” purchases for Black Friday. That’s not to say Prime Day shoppers ignore deals on luxury or “non-essential” items. There’s almost always an uptick in spending on cosmetics, apparel and tech during the event, which is balanced with spending on household basics and groceries, says Pandya.

Shoppers don’t know exactly what Amazon is discounting on Prime Day until the sale starts, which is part of the event’s allure. Prime Day bestsellers vary from year to year and from country to country, which isn’t just the result of different buying habits — deals in one country aren’t always reflective of another. But factors, like a discount being well-advertised or well-priced, can contribute to a product becoming a bestseller, as can Amazon’s agenda of selling as many of its devices as possible. Brands also use Prime Day to slash prices on soon-to-be out-of-season or out-of-style merchandise.

Some of the best Prime Day discounts are Amazon’s Lightning Deals, flash sales that give shoppers a short window to purchase limited quantities of specific products. Lightning Deals put shoppers in a competitive mindset and add what Steinman calls a “gamification” aspect to the sale. Shoppers don’t have time to think about whether they need the item being sold as a Lightning Deal, so they impulsively buy it because they don’t want to miss out.

By hosting Prime Day between the end of June and mid-July, Amazon permanently altered the retail calendar. It created the blueprint for a member-exclusive flagship summer sale, and proved that it’s powerful enough to create a halo effect on e-commerce by driving purchases to other sites as well as its own. That forced competitors like Walmart, Target, Macy’s and Best Buy to respond.

Since the first Prime Day in 2015, many retailers have changed the timing of their biggest sales to align with Amazon’s, or created new ones, like Walmart Deal Days and Target Circle Week. Amazon’s competitors hope that shoppers will spill over onto their sites and make additional purchases, which happens often. In 2026, 32 percent of Prime Day shoppers either shopped or planned to shop Target Circle Deal Days, and 49 percent either shopped or planned to shop the Walmart Deals event, according to Numerator.

“Amazon is in the driver’s seat, but retailers acknowledge that this is a real opportunity for them to capitalize on, so they need to employ all forces to help enable spending,” says Pandya.

Because Amazon moved Prime Day up to June in 2026, other retailers did the same with their summer sales. “Any really strong retailer is going to be a fast follower of what Amazon is doing and when, and piggyback onto the timing of its event,” says Murphy. “They’ll try to leverage that opportunity.”

For the first time in 2022, Amazon hosted two Prime Day-level events in one year: Prime Day in July and the Prime Early Access Sale in October. Amazon has followed that schedule ever since, but changed the name of the fall event to Prime Big Deal Days, although shoppers tend to refer to it as “October Prime Day.” This year, it’s taking place on October 6 and 7.

Shoppers originally didn’t see much of a difference between Prime Big Deal Days and Prime Day, but the retailer made them more distinct in 2025: It expanded the summer sale to be four-days and kept the fall sale to be 48 hours, creating a hierarchy where the longer sale is perceived as “better” than the shorter one.

Although hosting a second Prime Day-level event in the fall takes away some of the novelty the summer sale became known for, it’s Amazon’s attempt to kick off the holiday shopping season. Many of the retailer’s competitors now start their early Black Friday promotions in October to give shoppers extra time to buy gifts, a trend Steinman calls “seasonal shopping elongation.” Amazon wants to participate in this trend, so it added the October sale while still trying to recruit more Prime members, says Steinman. “It plays on shoppers’ fear of missing out on a great deal by creating the idea that member-exclusive events can take place at any point,” he says.

Amazon doesn’t disclose sales figures, so we don’t know exactly how Prime Big Deal Days compares to Prime Day in terms of revenue. Typically, however, discounts during the October event are lackluster compared to July, and people don’t feel the same level of pressure to shop, experts say. The summer isn’t filled with opportunities to take advantage of sales beyond Prime Day, which works in its favor. But shoppers know that Black Friday and Cyber Monday deals start as early as October across dozens of retailers, so they usually don’t approach Amazon’s fall savings event with urgency.

At NBC Selected, we work with experts who have specialized knowledge and authority based on relevant training and/or experience. We also ensure that all expert advice and recommendations are made independently and with no undisclosed financial conflicts of interest.

I’m a reporter at NBC Selected who has covered Amazon since 2020. I write about the retailer’s biggest sales (Big Spring Sale, Prime Day and Prime Big Deal Days) and frequently update NBC Selected’s Prime membership guide. I also regularly appear in related NBC News NOW and TODAY segments. For this article, I researched the history of Prime Day and spoke to three experts. I shared trends I’ve noticed first-hand over the years, too.

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Zoe MalinZoe Malin is a reporter for NBC Selected who leads coverage for tentpole sale events including Amazon Prime Day, Black Friday and Cyber Monday.