Let's say that you upgraded your cluster and noticed that the timezone of your AHV has changed, why and what is the recommended practice? 
When running a health check, you will see a warning stating that "The AHV host's time zone was changed/set to something other than UTC."

Nutanix recommends against making any configuration changes on the AHV hosts which includes changing timezone, from AHV version 20170830.58, the default timezone on AHV hosts is set to UTC upon upgrade or installation, for more information check out KB-6834

In this case, no further action is required from your side.

To edit the timezone of a user VM, check out KB-3134

To edit the timezone of a CVM, check out KB-1050