code: public void setTimeZone (final TimeZone timeZone)
    {
      if (m_aCronEx != null)
      {
        m_aCronEx.setTimeZone (timeZone);
      }
      m_aTimeZone = timeZone;
    }
docs: <p>
  Sets the time zone for which the <code>cronExpression</code> of this
  <code>CronTrigger</code> will be resolved.
  </p>
  <p>
  If {@link #setCronExpression(CronExpression)} is called after this method,
  the TimeZon setting on the CronExpression will "win". However if
  {@link #setCronExpression(String)} is called after this method, the time
  zone applied by this method will remain in effect, since the String cron
  expression does not carry a time zone!