I believe that I have found the source of the problem. The code which delegates off to the DateUtils.getDurationPretty(periodOffset, resourceBundle) method incorrectly passes the default resource bundle (which is the basic JIRA resource bundle), whereas it should actually be passing the regular resource bundle. I believe replacing the call in the prettyPrint() method from
return DateUtils.getDurationPretty(periodOffSet, i18n.getDefaultResourceBundle());
to
return DateUtils.getDurationPretty(periodOffSet, i18n.getResourceBundle());
will allow the Japanese translations to have effect on dates.
I believe that I have found the source of the problem. The code which delegates off to the DateUtils.getDurationPretty(periodOffset, resourceBundle) method incorrectly passes the default resource bundle (which is the basic JIRA resource bundle), whereas it should actually be passing the regular resource bundle. I believe replacing the call in the prettyPrint() method from
return DateUtils.getDurationPretty(periodOffSet, i18n.getDefaultResourceBundle());
to
return DateUtils.getDurationPretty(periodOffSet, i18n.getResourceBundle());
will allow the Japanese translations to have effect on dates.