The Changelog plugin generates reports based on the changes in the Software Configuration Management or SCM while the Changes plugin generates reports either from a changes.xml file or from the JIRA issue management system. For more information about the changes plugin, see http://maven.apache.org/plugins/maven-changes-plugin

According to Roger Pressman (in his book) Software Engineering: A Practitioner's Approach, SCM is a "set of activities designed to control change by identifying the work products that are likely to change, establishing relationships among them, defining mechanisms for managing different versions of these work products, controlling the changes imposed, and auditing and reporting on the changes made."

The dateFormat parameter is used when parsing the dates from the log entries retrieved from your SCM system. It can not be used to format the dates in the report. If you try to do this the parsed dates will be wrong and the dates in the report even more so. They can look like this 0020-05-27 for a file that was changed on 14 december 2005.