Dynamic desktop

Dynamic desktop is a feature introduced in macOS Mojave (10.14), in which the desktop background changes according to the time of the Mac's current location. If Location Services are turned off the Privacy pane of the System Preferences, then the time zone specified in the Date & Time preferences will be used.

Functionality
Supported versions of macOS use time and location data to calculate the position of the sun in relation to the user and then dynamically generate a desktop image from a series of images encoded in HEIC format.

Articles

 * How to create your own Dynamic Desktops in macOS Mojave by William Gallagher at AppleInsider (2018-10-01)
 * How to Use macOS Mojave's New Dynamic Desktop Feature by Juli Clover at MacRumors (2018-09-25)
 * The 3 Best Mac Dynamic Wallpaper Sites (And How to Make Your Own) by Shubham Agarwal at MakeUseOf (2019-12-16)
 * Yes, you can get more Dynamic Desktop wallpapers for Mojave. Here's how. by Stan Schroeder at Mashable (2018-09-28)