We should only use the isoOffsetFormat() version of offset name for QLocale::C - while other locales may coincide with it, we don't know so shouldn't just assume. Add a query for whether a locale is the one used by the backend for the abbreviation in its data() and, when it is, use that abbreviation as short name. The TZ backend was searching its transitions for help with the abbreviation; we can do that also in the base-class, so introduce a data(TimeType) that will search transition history (if available) for a suitable transition from which to take the abbreviation (when appropriate). This shall make displayName() return an empty string in various cases where it did not, before; this is more honest than returning a string that's inappropriate for the locale for which it was meant to be answering. Task-number: QTBUG-114914 Task-number: QTBUG-115158 Task-number: QTBUG-122448 Change-Id: I523229def63aafcd2009b8406b2c3d13f7c01d9c Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>