This year's Amazon Prime Day is reportedly scheduled to start around midday July 16 and continue through the following day.

The unannounced date was accidentally published on a banner of Amazon's U.K. website this week, according to TechRadar.

Amazon didn't immediately respond to CNBC's request for comment nor confirm the date to TechRadar.

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A day and a half of deals would make this year's Prime Day the longest one yet for Amazon. In 2017, the event ran for a little more than 24 hours. Prime Day didn't get its start until 2015.

The online shopping extravaganza — much like Amazon's version of Black Friday or Cyber Monday — in 2017 was the biggest one yet. Sales grew by more than 60 percent from the prior year, the company said. The event also helped the company add "tens of millions" of new, paying Prime members to its platform.

Speculation was already swirling this month that Amazon would hold Prime Day 2018 closer to July 10, based on past events. In 2015, Prime Day fell on July 15. In 2016, it was held on July 12. And last year the deals kicked off on July 10.

For other retailers, Prime Day has sparked a slew of rival shopping events.

Last year, for example, Target kicked off its back-to-school deals the same week of Prime Day, while J.C. Penney held a "Penney Palooza" sale online.

Often some of the best deals on Amazon.com during Prime Day are for Amazon's own devices, such as the Echo, Kindle, and Fire TV Stick. This year, however, the e-commerce giant is expected to make a bigger push in grocery and apparel, with Whole Foods merchandise and more apparel brands (i.e. Nike and Calvin Klein) selling through the website.

WATCH: Amazon and Whole Foods, one year later