iOS 13 is faster and more responsive with optimizations across the system that improve app launch, reduce app download sizes and make Face ID even faster. Dark Mode is available to third-party app developers for integration into their own apps and can be scheduled to turn on automatically at sunset or at a certain time. Photos curates the entire library to highlight the best images, hiding clutter and hiding similar photos to showcase significant events from the past day, month or year. Photos and videos are intelligently organized, making it easier to browse, discover and relive favorite memories.”]
Source: https://www.apple.com/newsroom/2019/06/apple-previews-ios-13/