One glaring omission when Apple introduced Dark Mode in macOS Mojave was the option to automatically turn the feature on and off depending on the time of day. But with the upcoming release of macOS Catalina, the company finally rectified this. There is now an Auto Dark Mode option. You can head to System Preferences – General to see the three options: Light, Dark, and Auto. If you choose Auto, the different design elements on your desktop will get darker at night and then get lighter during the day. Complementing this feature is the Dynamic Desktop wallpaper, which changes depending on the time of day. As expected, there will be a Santa Catalina Island option that will launch when macOS Catalina launches in the fall.
Source: Mashable