September

September belongs to teachers, engineers, and a cluster of major UN observances tied to peace, literacy, and biodiversity.

• 5 September — Teachers' Day, marking the birth anniversary of Dr Sarvepalli Radhakrishnan (born 5 September 1888), India's first Vice-President and second President, a philosopher and academic — when some of his former students asked to celebrate his birthday, he reportedly requested that the day instead be observed to honour all teachers, and it has been observed as such since 1962.
• 8 September — International Literacy Day, proclaimed by UNESCO in 1966, marking the anniversary of the opening of the World Congress of Ministers of Education on the Eradication of Illiteracy, held in Tehran in 1965.
• 14 September — Hindi Diwas, marking the date in 1949 that the Constituent Assembly of India adopted Hindi in the Devanagari script as one of the official languages of the Union — distinct from World Hindi Day (10 January), which marks the first World Hindi Conference of 1975 (see Commonly Confused Days for the full contrast).
• 15 September — Engineer's Day, marking the birth anniversary of Sir Mokshagundam Visvesvaraya (born 15 September 1861), the celebrated civil engineer and statesman behind the Krishna Raja Sagara Dam and numerous flood-control and irrigation systems, recipient of the Bharat Ratna.
• 16 September — World Ozone Day, marking the date in 1987 that the Montreal Protocol on Substances that Deplete the Ozone Layer was signed — widely regarded as one of the most successful international environmental agreements ever adopted.
• 21 September — International Day of Peace, established by the UN General Assembly in 1981 and later fixed to this specific date in 2001, dedicated to strengthening the ideals of peace both within and among all nations and peoples — observed with the ringing of the "Peace Bell" at UN Headquarters.
• 22 September — World Rhino Day, launched in 2010 by the World Wildlife Fund's South Africa office, celebrating all five species of rhinoceros and raising awareness of the threats they face, particularly poaching.
• 26 September — World Contraception Day, promoted by a coalition of international organisations to raise awareness of contraception and improve reproductive health knowledge among young people.
• 27 September — World Tourism Day, marking the date in 1970 that the statutes of the UN World Tourism Organization (UNWTO) were adopted — the choice of date was also meant to mark the end of the high tourist season in the Northern Hemisphere and the start of it in the Southern Hemisphere.

Memory hook — "Radhakrishnan asked, so we honour every teacher": the single most-repeated origin story in this whole book — Teachers' Day exists because Dr Radhakrishnan redirected his own birthday celebration outward, onto the profession he'd spent his life in, rather than accepting personal tribute.

Practice Recall: Explain, without checking, the difference between World Hindi Day and Hindi Diwas — the sponsoring context, the year, and the specific event each marks.