September 16 Holidays

Mexican Independence Day marks the “Grito de Dolores” delivered by Father Miguel Hidalgo on the night of September 15–16, 1810, from the church of Dolores, Guanajuato — the rallying cry that launched Mexico’s independence movement, formally ending Spanish colonial rule in 1821. International Day for the Preservation of the Ozone Layer was established by the UN General Assembly to mark September 16, 1987, when the Montreal Protocol on Substances that Deplete the Ozone Layer was opened for signature — the only treaty in UN history to achieve universal ratification, widely regarded as the most successful environmental agreement ever. National Play-Doh Day celebrates the modeling compound invented by Noah McVicker in the early 1950s as a wallpaper-cleaning putty, repurposed for children’s play after his sister-in-law used it as a craft material in her nursery school class in Cincinnati. National Cinnamon Raisin Bread Day celebrates the enriched bread studded with plump raisins and dusted with cinnamon — a yeasted American bakery staple whose combination traces to 19th-century spice trade accessibility.