Mass. Gen. Laws ch. 6 § 15QQQQQQ
The governor shall annually set apart December 13, the anniversary of the founding of the National Guard, in recognition of its role as an operational reserve of the United States Army and Air Force, providing ready, well-equipped personnel and equipment to support the federal military mission when called upon by the President and the governor of the commonwealth to respond to domestic emergencies, and by the citizen soldiers and airmen of the commonwealth who have unfailingly answered the call of duty, and shall issue a proclamation recommending that the day be observed by the people in the display of the flag and in appropriate public exercises, commemorative of the services and sacrifices of the citizens of the commonwealth who have served and continue to serve in the defense of the United States.
Mass. Gen. Laws ch. 6, § 15QQQQQQ