Your society's constitution is a private contractual agreement among members. The holding of an Annual General Meeting is a rule in your society's constitution. Your members must agree to any changes in the month the Annual General Meeting is supposed to be held. If the change is to be permanent, the members would have to pass a resolution at a General Meeting to change the rule. Thereafter, an application to amend this rule must be made to the Registry of Societies. The change has to be approved by the Registry of Societies before it can be adopted by the society.