Arbor Day was first celebrated in Spain in 1594 with the planting of a poplar tree in the village square during wartime. In 1872, the first Arbor Day was celebrated in America, when 1 million trees were planted in Nebraska. Soon after, the American Forestry Association campaigned for a national holiday, and also planted the idea in Europe, Australia and Canada. Arbor Day is now celebrated around the world, with varying dates according to local climate conditions.
Find out more: https://www.arborday.org/celebrate/