India annually celebrates Hindi Diwas across schools, colleges and offices to promote the use of Hindi language in the country. Hindi Diwas is observed on September 14. On this day, the government arranges various programmes highlighting the importance of Hindi. But do you know why it is observed on this date? On September 14, 1949, the Constituent Assembly had adopted Hindi written in Devanagari script as the official language of the Republic of India.