Which party observed the “Black Day” on July 3, 1947 against Partition of India?

Q. Which party observed the “Black Day” on July 3, 1947 against Partition of India?
Answer: Hindu Mahasabha
Notes: Black Day was observed by Hindu Mahasabha on July 3 , 1947 to express resentment regarding partition of India. The observation met with considerable success in Maharashtra - in Bombay , Poona and Sholapur .