Step 1: Understand "Foundation Day" or "Statehood Day".
This day marks the date on which a territory was officially granted the status of a full-fledged state within the Union of India.
Step 2: Recall the history of Mizoram's statehood.
Mizoram was previously a district of Assam. After a long period of insurgency led by the Mizo National Front (MNF), a historic peace accord, the Mizoram Peace Accord, was signed between the Government of India and the MNF in 1986.
Step 3: Identify the date of statehood.
Following the accord, the Indian Parliament passed a constitutional amendment, and Mizoram became the 23rd state of India. This officially happened on February 20, 1987. This date is celebrated annually as Mizoram's Statehood Day.