Step 1: Recall the fact:
8 March is observed as International Women's Day, and the United Nations adopted its first official annual theme for the day in 1996 ('Celebrating the Past, Planning for the Future').
Step 2: Match with the options:
Of the years given, 1996 is the one that marks the start of this themed observance, so it is the correct choice.
Final Answer:
8th March, 1996