Step 1: Recall the role of the Model Code of Conduct (MCC).
The MCC is a set of guidelines issued by the Election Commission of India to regulate the conduct of political parties and candidates during elections to ensure free and fair polling.
Step 2: Identify when MCC comes into force.
The MCC comes into immediate effect from the date and time the Election Commission officially announces the election schedule (dates of notification, nomination, polling, and counting).
Step 3: Confirm the trigger event.
It is not triggered by filing nominations, withdrawal of nominations, or announcement of results, but specifically by the announcement of the election schedule by the Election Commission.
\[ \boxed{\text{On the day of announcement of election schedule}} \]