Here’s where to download them:

Mac users - download here! Each season has 2 dynamic wallpapers - one for daylight savings time and another for standard. Individual jpegs for every phase are also included here.

If they don’t work try changing to another wallpaper then back to the dynamic one, restarting your computer or waiting a day/until the next phase is set to start.

Windows users - available on Wallpaper Engine!
SPRING | SUMMER | AUTUMN/FALL | WINTER

Artsist also uploaded the original version from Feb to Wallpaper Engine too, since I never actually uploaded it there myself!

Phone users - download here! Not dynamic though, just the individual wallpaper jpegs resized to fit phones better.