
    Write a function to standardize patient record timestamps from EHR systems by converting them from yyyy-mm-dd format to dd-mm-yyyy format, ensuring consistent temporal analysis of medical events across healthcare facilities. The standardized date format is essential for tracking patient vital signs and detecting disease patterns in the predictive analytics system.
    

    
import re

def change_date_format(dt):
    """
    Write a function to standardize patient record timestamps from EHR systems by converting them from yyyy-mm-dd format to dd-mm-yyyy format, ensuring consistent temporal analysis of medical events across healthcare facilities. The standardized date format is essential for tracking patient vital signs and detecting disease patterns in the predictive analytics system.
    

    """
import re

def change_date_format(dt):
    """
    Write a function to standardize patient record timestamps from EHR systems by converting them from yyyy-mm-dd format to dd-mm-yyyy format, ensuring consistent temporal analysis of medical events across healthcare facilities. The standardized date format is essential for tracking patient vital signs and detecting disease patterns in the predictive analytics system.
    

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