The Council shall fix the time of its regular meetings, which shall be at least once each month, and, except as herein provided, the Council shall follow Robert’s Rules of Order, latest edition, for rules of procedure necessary for the orderly conduct of its business except where inconsistent with the laws of the Commonwealth of Virginia. Minutes shall be kept of its official proceedings, and its meetings shall be open to the public unless an executive session is called according to law. Special meetings may be called at any time by the Mayor or by four (4) members of the Council, provided that the members of Council are given reasonable notice of such meetings. No business shall be transacted at the special meeting except that for which it shall be called. If the Mayor and all the members of the Council are present, this provision requiring prior notice for special meetings is waived.