Step 1: Distinguish adopted vs enforced:
The Constituent Assembly formally adopted and signed the Constitution of India on 26 November 1949, which is why that date is now observed as 'Samvidhan Divas' (Constitution Day).
Step 2: The other key date:
The Constitution came into force/effect on 26 January 1950 (Republic Day) — a different event from adoption, chosen to coincide with the 1930 Purna Swaraj declaration.
Step 3: Why the others are wrong:
15 August 1947 is Independence Day, and 30 January 1952 has no constitutional significance (it marks Gandhi's assassination anniversary observed as Martyrs' Day, unrelated).
Step 4: Final Answer:
26 November, 1949 — the date of adoption, as the question specifically asks.