docs: public static final Map<String, DateTimeZone> getDefaultTimeZoneNames() {
          Map<String, DateTimeZone> names = cZoneNames.get();
          if (names == null) {
              names = buildDefaultTimeZoneNames();
              if (!cZoneNames.compareAndSet(null, names)) {
                  names = cZoneNames.get();
              }
          }
          return names;
      }