Each artifact uploaded to Maven Central has a last modified time associated with it. You can see an example of this by drilling into an artifact's details on search.maven.org.
How do I retrieve an artifact's last modified time using Aether?
I am retrieving this information purely for human consumption (i.e. "How long ago did this project make a release? Is it being actively maintained?").
One way to retrieve this information (though not officially supported) is to construct the Artifact's URI and issue an HTTP HEAD to retrieve the Last-Modified header.
I'm not aware of any official API to do this (suggestions welcome!)