Have you marked your calendar? the alleged date of the online retailers annual Prime Day ...has been leaked. An image on the Amazon U.K. site was spotted by TechRadar and revealed July 16th as the start date for the annual summer sales event. And Amazon is doing something new with this year's Prime Day- it's actually going to be a 36-hour sale as opposed to prior year's 30-hour extravaganza with deals starting at noon on July 16th and going through the 17th.