Revenue bonds shall be dated as of the date of the resolution or order of the board of directors authorizing their issuance. The board of directors may use any available moneys of the district, not already allocated to some other purpose, for the payment of any interest or principal due or past due on any revenue bonds of the district, and may advance moneys of the district for such purposes and in the event of such advancement shall be entitled to reimbursement in the amount thereof out of any levies thereafter made or any moneys thereafter collected and applicable to the payment of such bonds.