Which three states celebrate their Foundation Days ?

Three northeastern states of Tripura, Manipur and Meghalaya celebrate their foundation day.The erstwhile princely states of Tripura and Manipur were merged with India in October 1949 and became full-fledged states on January 21, 1972. Meghalaya was part of Assam before becoming a full-fledged state under the North Eastern Region (Re-Organisation) Act, 1971.