John Martin has an interesting use case for tagging in Terraform:
One of the key properties missing from Azure resources, in my opinion anyway, is a CreatedDate. This can be largely overcomes with Azure policy, but what if you don’t have access to create one that applies a timestamp tag at resource creation?
It is possible to use Terraform to tag the resource and set the value for when the resource is created. There is a little more work that needs to go into it to ensure that once it is set that Terraform does not overwrite it on subsequent deployments. But, it is achievable and brings this into your control if needed.
Click through to see how.