Time measure in icon map

Good morning to y'all 

I hope everyone's doing well, i want to make a question about the usage of a time count in the icon map custom visual
I work in a timber company and we are planning to make a dashboard focused in areas where we planted eucalyptus trees, in the dashboard we want to show two different graphs one with the newly planted trees and the other showing the one's with 2 years or more since they were planted, do i need to make the metrics in some specific way or i can just put them and that's it ? 

Since now thanks for the help!!