docs: public BaseField getHistorySourceDate()
      {
          if (m_fldSourceHistoryDate == null)
          {
              if (m_iSourceDateSeq != null)
                  m_fldSourceHistoryDate = this.getOwner().getField(m_iSourceDateSeq);
              else if (this.getHistoryRecord() instanceof VirtualRecord)
                  m_fldSourceHistoryDate = this.getOwner().getField(VirtualRecord.LAST_CHANGED);
          }
          return m_fldSourceHistoryDate;
      }