Amazon's (AMZN -1.12%) recent stock split put the retail giant in the spotlight. After years of trading higher than $1,000 a share, the stock was about to settle at a price of $124.

Stock splits don't change the overall market value of a company. They just lower the value of each individual share through the issuance of more stock to current holders.

The lower share price makes it easier for a broader range of investors to buy. Investors haven't yet flocked to Amazon, though. The shares have slipped about 9% since the June split. So the split hasn't been a catalyst for the stock.

Another catalyst is on the horizon, however. And it's likely to top the stock split, by far.

A two-day sales event

I'm talking about Amazon's Prime Day. This year's mega-sales event is set for July 12 through July 13 in more than 20 countries. Amazon and third-party sellers on the platform feature bargains on a variety of items, exclusively for Prime members. And early Prime Day deals have already started -- such as discounts of as much as 60% on Amazon devices.

Last year, the event generated more than $11 billion in sales. That's up from about $10 billion in 2020 and $7 billion in 2019. In fact, sales have climbed from year to year since the first Prime Day back in 2015, according to Digital Commerce 360. Amazon said shoppers globally bought more than 250 million items during last-year's Prime Day. And customers spent $1.9 billion on items from third-party sellers during pre-Prime Day promotions.

Prime Day happened during Amazon's second quarter last year. Just to get an idea of how big this event is, let's compare the Prime sales figure with Amazon's total second-quarter sales figure. The sales generated during the event represented nearly 10% of Amazon's total quarterly sales. That's huge, considering that Prime Day lasts only two days.

A challenging environment

Prime Day is particularly important for Amazon this time around. Like most retailers, Amazon has been struggling with higher inflation and supply chain issues. This weighed on first-quarter earnings. Operating cash flow and operating income declined.

All of this has hurt investor sentiment. So it's understandable some investors didn't rush to buy Amazon shares after the stock split. The Prime Day event gives Amazon an opportunity to win back investors' confidence.

So far, even in a difficult environment, Amazon's sales have continued to climb. For instance, in the first quarter, sales rose 7% to more than $116 billion. If Amazon is able to keep momentum going during Prime Day, we might see a positive impact on earnings.

Amazon also has grown Prime membership during these troubled times. It added millions of Prime members in the first quarter. The company also said member renewal rates remain high.

Prime Day is likely to offer Amazon a membership boost. In the past, it's been a time when people sign up for the service. For example, back in 2015, Amazon gained more than 700,000 members just on Prime Day, according to Clarus Commerce.

More revenue and members

Prime Day could bring Amazon a wave of sales and an increase in Prime membership. Both of these elements are good for earnings. And a solid -- or even improving -- earnings report could encourage investors to add Amazon shares to their portfolios.

The stock split was good news for investors who couldn't buy Amazon shares at a thousand-dollar share price. But it didn't change anything about Amazon's revenue picture or future prospects. Prime Day does. If sales continue to climb from last-year's level, it's a clear sign demand remains high.

The addition of new Prime members should also lead to more revenue down the road because members tend to stick around. About 98% of Amazon Prime members renewed for a second year in the first quarter of last year, according to Statista.

All of this means investors should keep an eye on Prime Day. It may not lift Amazon shares immediately. But if it's successful, it could help boost earnings and shares over time.