They are made Prefects of Slytherin House.
Although we do know that Ron and Hermione received their Prefect badges on August 31, we don't know if Pansy and Draco also received theirs the same day, so we'll put this date as just August.
Draco Malfoy and Pansy Parkinson are made prefects
Date August, 1995
Certainty Inferred from canon
Location in Canon OP9
Type of Event Wizarding world