docs: public static DateTimeZone getDefault() {
          DateTimeZone zone = cDefault.get();
          if (zone == null) {
              try {
                  try {
                      String id = System.getProperty("user.timezone");
                      if (id != null) {  // null check avoids stack overflow
                          zone = forID(id);
                      }
                  } catch (RuntimeException ex) {
                      // ignored
                  }
                  if (zone == null) {
                      zone = forTimeZone(TimeZone.getDefault());
                  }
              } catch (IllegalArgumentException ex) {
                  // ignored
              }
              if (zone == null) {
                  zone = UTC;
              }
              if (!cDefault.compareAndSet(null, zone)) {
                  zone = cDefault.get();
              }
          }
          return zone;
      }