
    Write a function to convert a user's social network registration date from the database storage format (yyyy-mm-dd) to a user-friendly display format (dd-mm-yyyy) for showing member join dates in connection recommendations. The function should handle any valid registration date since the platform's launch and maintain the exact day, month, and year information in the conversion process.
    

    
import re

def change_date_format(dt):
    """
    Write a function to convert a user's social network registration date from the database storage format (yyyy-mm-dd) to a user-friendly display format (dd-mm-yyyy) for showing member join dates in connection recommendations. The function should handle any valid registration date since the platform's launch and maintain the exact day, month, and year information in the conversion process.
    

    """
import re

def change_date_format(dt):
    """
    Write a function to convert a user's social network registration date from the database storage format (yyyy-mm-dd) to a user-friendly display format (dd-mm-yyyy) for showing member join dates in connection recommendations. The function should handle any valid registration date since the platform's launch and maintain the exact day, month, and year information in the conversion process.
    

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