The term ‘secular’ was added to the Preamble of the Constitution

Originally, the Preamble described India as a sovereign, democratic republic.
In 1976, during the Emergency period, the 42nd Amendment Act was passed.
This amendment inserted the words “socialist” and “secular” into the Preamble, making it read:
“We, the people of India, having solemnly resolved to constitute India into a Sovereign Socialist Secular Democratic Republic…”
The purpose was to emphasize that India does not favor any religion and treats all religions equally, ensuring freedom of faith and belief for its citizens.
So, the correct year is 1976