What is necessary to change the bid date?

An addendum is necessary to change the bid date because it serves as an official communication that modifies the original bid documents. When an addendum is issued, it provides updated information to all bidders, ensuring that everyone has the same access to the new bid date and any other changes made to the bidding process. This maintains transparency and fairness in the bidding procedure.

The other options do not fulfill the requirement for changing a bid date. A change order typically involves modifications to an existing contract after the award, which would not be applicable before the bidding takes place. A construction change directive relates to changes that occur after a project has started and is issued at the request of the owner or architect, making it irrelevant in the context of pre-bid processes. A memo to bidders could communicate changes but does not have the official standing that an addendum carries, which is specifically recognized in contract law and project bidding protocols.