Any resolution providing for the levy of assessments for payment of debt service on bond debt or notes, or for the long-term maintenance of natural habitat, or any hearings upon the formation of a district, or upon the levy of annual assessments after formation of a district shall be concluded and any resolution confirming a diagram and an assessment shall be adopted not later than either of the following dates:
(a) July 1 of the fiscal year during which the assessments are to be collected on the county assessment roll.
(b) A later date, not beyond the third Monday in August, that the county auditor authorizes.