Section 100. Mandatory referendum

When  a  resolution of the board of
  supervisors is subject to a mandatory referendum, such  board  shall  by
  resolution  cause  such  resolution  to  be  submitted  to a vote of the
  qualified electors of the county for their approval or disapproval at  a
  general  or  special  election. Except as otherwise provided by law, the
  resolution shall fix a date not less  than  forty-five  days  after  its
  adoption  on which the proposition is to be submitted at such general or
  special election.