"On June 26, 1975, prime minister Indira Gandhi announced on the All India Radio that “the president has proclaimed Emergency.” .... The 42nd amendment came soon after. This 20 pages long detailed document gave unprecedented powers to the Parliament. Almost all parts of the Constitution, including the preamble, was changed with this amendment. Thereafter the description of India in the preamble was changed from “sovereign, democratic republic’ to a ‘sovereign, socialist, secular, democratic republic.”"
January 1, 1970
https://en.wikiquote.org/wiki/Secularism_in_India