The reference date for the census is October 1, 2020 for Jammu and Kashmir and snow bound areas of Himachal Pradesh and Uttarakhand, while for the rest of country is March 1, 2021.
"In exercise of the powers conferred by section 17A of the Census Act, 1948 (37 of 1948), the central government hereby extends the provisions of the said Act, for conduct of a pre-test of the Census of India, 2021.
"The pre-test shall be conducted from August 12, 2019 to September 30, 2019 in all the states and the Union Territories," Joshi said in a notification.
For the first time in the 140-year history of the census in India, data is proposed to be collected through a mobile app and enumerators would be encouraged to use their own phone.
The census 2021 will be the world's largest enumeration exercise, an official said.
A total of 33 lakh enumerators, the persons who conduct door-to-door counting, would be mobilised for data collection for which notification has already been issued.
Union Home Secretary Rajiv Gauba had said the census is not only an exercise of head count, but also provides invaluable socio-economic data which forms credible basis for informed policy formulation and allocation of resources.
The changing demographics and socio-economic parameters reflected by the census helps in reformulation of the country's plans for the economic development and welfare schemes for its people, Gauba had said.
The Census 2021 will be conducted in two phases. In the first phase, house listing operations would be conducted in any two months chosen by the states between April and September in 2020.
In the second phase, actual population enumeration would be done during February 9 to 28, 2021, followed by the revision round from March 1 to 5, 2021.
In Jammu and Kashmir and snow bound areas of Himachal Pradesh and Uttarakhand, population enumeration would be conducted during September 11 to 30, 2020, followed by the revision round from October 1 to 5, 2020.