https://www.pcgamer.com/leak-reveals-amazon-prime-day-2018-will-see-36-hours-of-deals-starting-july-16/

You're not supposed to know this yet, but Amazon's Prime Day 2018 is scheduled to go live on Monday, July 16, just over three weeks from now, and will last for a full 36 hours. Amazon hasn't officially said any of this yet, but our sister site TechRadar stumbled across an Amazon Prime Day 2018 banner on the Amazon UK website.

Presumably published in error, a visit to Amazon UK's Prime page now shows a banner that simply says "Coming Soon," without any mention of a date or how long it will last. But unless someone at Amazon is trying to throw everyone off the company's trail, you're safe to mark your calendars and plan accordingly.