release-history.json in the update center captures the history of every version of every Jenkins plugin ever released to the Jenkins update center.
The whole file is essentially an array of the following entry, which represents releases of plugins in a given day:
The 'timestamp' field is a number of milliseconds since the epoch.
The 'gav' field refers to the Maven groupId/artifactId/version triplet that identifies the Maven release that became the plugin. You can use GAV-Repository mapping to further tie this to the buildable source tree.