The Indian postal service system was brought into force on this day.
According to The Post Office of India and its Story, written by Geoffrey Clarke, who had been appointed Postmaster General of Bengal and Assam in 1917 and Director General of Posts and Telegraphs for British India (including Aden, Burma and Ceylon) in 1918: “Under the administration of Warren Hastings the Post Office in India was placed on a better footing and steps were taken to make the posts which were established for official purposes more generally available for private communications.”
The Calcutta General Post Office opened on the same day, the India Post website says.