Step 1: Understand the change.
India recently replaced three old criminal laws with three new ones. The old Code of Criminal Procedure, 1973 was replaced by the Bharatiya Nagarik Suraksha Sanhita (BNSS), 2023. The question asks the exact date this new law came into force.
Step 2: Note the group of new laws.
Three new laws came together: the BNS (replacing the IPC), the BNSS (replacing the CrPC), and the BSA (replacing the Evidence Act). All three were brought into force on the same date.
Step 3: Recall the notified date.
The Government of India notified that these three new criminal laws would start working from 1 July 2024. So that is the commencement date for the BNSS.
Step 4: See the effect.
From 1 July 2024, the old Code of Criminal Procedure, 1973 stood repealed and the BNSS took its place for new matters.
Step 5: Remove the wrong dates.
January 1, 2024, December 25, 2023, and August 15, 2023 are not the commencement dates. The laws were passed in 2023 but only came into force on the notified day in 2024.
Step 6: State the answer.
So the BNSS came into force on July 1, 2024. \[ \boxed{\text{July 1, 2024}} \]