Section 4. Proclamation of Arbor Day. —

All provinces, cities and municipalities with their component barangays shall be required to declare an Arbor Day or Tree Planting Day by appropriate proclamation of their respective local chief executive through an ordinance passed by the respective local sanggunian, at a fixed date every calendar year as shall be deemed conducive to the proper time and season for planting trees in the respective localities. Although adoption of uniform dates for its celebration shall be encouraged, varying dates may be allowed in order to afford flexibility in the planning and implementing of the programs for tree planting: Provided, That the Arbor Day designated shall be declared as a public working holiday in order to ensure the participation of the different sectors of society and such declaration may be embodied in the proclamation that local chief executives are authorized to do under this Act.