Why did Constitution come into force 2 months post adoption?

The Constitution of India was adopted by the Constituent Assembly on November 26, 1949, which is now celebrated as Constitution Day. However, it was enforced on January 26, 1950, to commemorate the declaration of Purna Swaraj. The Indian National Congress had, on that day, in 1930 proclaimed full independence from the British rule, thereby rejecting the dominion status they offered.