Symptom: ERROR [atlassian.core.util.DateUtils] java.util.MissingResourceException: Can't find resource for bundle java.util.PropertyResourceBundle, key core.dateutils.day

ConfluenceActionSupport.properties is missing definitions for the singular properties = it has weeks, days, hours, minutes and seconds, but not week, day, hour or second (somehow, though, it has "minute" already)