The 35-day long mega campaign will feature a second phase of the census in Bihar starting from January 25th, allowing individuals to register their details until 15 days prior.

Here is the translation of the given Hindi text into English: A 35-day mega campaign: The second phase of the census in Bihar will begin on January 25, allowing people to register their details themselves until 15 days prior. This means the second phase of the census in Bihar will run from January 23 to February 28, spanning 35 days. Before this, the general public will have the opportunity to register their details themselves for 15 days. People will answer 40 questions online by visiting the `censusindia.gov.in` portal. After that, they can send the received message (message) to their mobile.