https://github.com/jenkinsci/jenkins/blob/dd6ddd259fbdee960d1dd68562feec8e29ac22f6/war/src/main/js/templates/plugin-manager/available.hbs#L70-L72 always renders US (or the Jenkins controller's) localized date format, instead of the browser's, or a locale-independent format.

Additionally, ideally more than date resolution would be provided, for recent plugin releaes "22 hrs ago" is a much more specific value than provided in the tooltip (when I'd expect a tooltip to be more detailed, not less). Since we expect admins to keep their instances generally up to date, we should expect "hrs ago" or "days + hrs ago" to be the most common occurrence.