Quoc: The preamble has been amended only once so far. On 18 December 1976, during the Emergency in India, the Indira Gandhi government pushed through several changes in the Forty-second Amendment of the constitution. A committee under the chairmanship of Sardar Swaran Singh recommended that this amendment be enacted after being constituted to study the question of amending the constitution in the light of past experience. Through this amendment the words "socialist" and "secular" were added between the words "Sovereign" and "democratic" and the words "unity of the Nation" were changed to "unity and integrity of the Nation".

Answer this question based on the passage: when was the preamble of the indian constitution amended?
HW Chung: OK, some thoughts:
The important part for answering this question is: On 18 December 1976, during the Emergency in India, the Indira Gandhi government pushed through several changes in the Forty-second Amendment of the constitution. The answer is 18 December 1976.