This is an early access version of Gaia featuring the upcoming HDRP Time of Day System for Gaia Pro 2021. It features fully configurable Time Of Day Lighting, HDRP volumetric clouds and weather effects.
You can download this Early Access Version as part of your Canopy Pro Subscription and use it as you regularly would use Gaia. The system requires Unity 2021.2 HDRP.
If you install over an existing Gaia installation, please make sure to remove the folder Procedural Worlds\Gaia\Gaia Pro\HDRP Time Of Day first - this folder contains an older version of the system that will create conflicts if it is being kept around. If you accidentally installed over without deleting the folder first, delete the folder now and re-import the Early-Access Version again. This should fix it.
For more details regarding using the Time of Day System, please see the library article here: