National Mathematics Day is celebrated in India every year on December 22nd to commemorate the birth anniversary of mathematician Srinivasa Ramanujan. Some of the key ways this day is celebrated include workshops and lectures discussing Ramanujan's contributions to mathematics, encouraging students to learn more about fields like trigonometry, and paying tribute to Ramanujan's achievements and influence on mathematics. This day aims to celebrate Ramanujan's legacy and importance and inspire further learning and achievement in mathematics.