International Ozone day is celebrated on ........

Explanation:

16 September

• In 1994, the United Nations General Assembly proclaimed 16 September the International Day for the Preservation of the Ozone Layer, commemorating the date of the signing, in 1987, of the Montreal Protocol on Substances that Deplete the Ozone Layer (resolution 49/114)
• The photochemical mechanisms that give rise to the ozone layer were discovered by the British physicist Sydney Chapman in 1930.