Jenkins started with the following system properties:

      - arg[3]: `-Dfile.encoding=SJIS`
      - arg[4]: `-Dsun.jnu.encoding=SJIS`
      - arg[5]: `-Duser.language=ja`
      - arg[6]: `-Duser.timezone=Asia/Tokyo`

this results in duration printed like this:

  * Process uptime: 17 日

As far as I understand, the bundle is produced in UTC and non-localized to minimize variability and enable at least partial automatic processing. Hence durations should be localized.