We would like to track the history of values in Start Date, Completion Date and Target Date fields on Case Milestones. I couldn't find any documentation about this on Salesforce Documentation site. Is there a Standard functionality to do this? or should use APEX to achieve this?
Salesforce doesn't provide options to track histories for CaseMilestone object.
You need to create a custom object and store the values of each individual fields which you want to track.
Refer Field History Tracking
You can track the field history of custom objects and the following standard objects.
- Contract line items
- Order Products
- Service Contracts