
    Write a function to convert student assessment completion dates from the learning platform's database format (yyyy-mm-dd) to the regional reporting format (dd-mm-yyyy) for displaying in student progress reports. The function should handle any valid completion date stored in the system and maintain the chronological accuracy of student performance data.
    

    
import re

def change_date_format(dt):
    """
    Write a function to convert student assessment completion dates from the learning platform's database format (yyyy-mm-dd) to the regional reporting format (dd-mm-yyyy) for displaying in student progress reports. The function should handle any valid completion date stored in the system and maintain the chronological accuracy of student performance data.
    

    """
import re

def change_date_format(dt):
    """
    Write a function to convert student assessment completion dates from the learning platform's database format (yyyy-mm-dd) to the regional reporting format (dd-mm-yyyy) for displaying in student progress reports. The function should handle any valid completion date stored in the system and maintain the chronological accuracy of student performance data.
    

    """
    return re.sub('(\\d{4})-(\\d{1,2})-(\\d{1,2})', '\\3-\\2-\\1', dt)