docs: public long convertUTCToLocal(long instantUTC) {
          int offset = getOffset(instantUTC);
          long instantLocal = instantUTC + offset;
          // If there is a sign change, but the two values have the same sign...
          if ((instantUTC ^ instantLocal) < 0 && (instantUTC ^ offset) >= 0) {
              throw new ArithmeticException("Adding time zone offset caused overflow");
          }
          return instantLocal;
      }