BOULDER, Colo.--(BUSINESS WIRE)--Outside Interactive Inc., in partnership with the State of Colorado's Outdoor Recreation Industry Office and presented by Capital One and REI Co-op, today announced that Outside Days, previously known as Outside Festival & Summit, will return to downtown Denver from May 28 – 31, 2026, and feature headliners Death Cab for Cutie, My Morning Jacket, Cage The Elephant, Tash Sultana, Goth Babe, Japanese Breakfast, The Flaming Lips, Dawes, and more. Outside Days i. ...