def __validate_dates(start_date, end_date):
    """Validate if a date string.

    Validate if a string is a date on yyyy-mm-dd format and it the
    period between them is less than a year.
    """
    try:
        start_date = datetime.datetime.strptime(start_date, '%Y-%m-%d')
        end_date = datetime.datetime.strptime(end_date, '%Y-%m-%d')
    except ValueError:
        raise ValueError("Incorrect data format, should be yyyy-mm-dd")
    if (end_date - start_date).days > 366:
        raise ValueError("The difference between start and end date " +
                         "should be less than or equal to 366 days.")
    if (end_date - start_date).days < 0:
        raise ValueError("End date cannot be before start date.")
def __validate_dates ( start_date , end_date ) : try : start_date = datetime . datetime . strptime ( start_date , '%Y-%m-%d' ) end_date = datetime . datetime . strptime ( end_date , '%Y-%m-%d' ) except ValueError : raise ValueError ( "Incorrect data format, should be yyyy-mm-dd" ) if ( end_date - start_date ) . days > 366 : raise ValueError ( "The difference between start and end date " + "should be less than or equal to 366 days." ) if ( end_date - start_date ) . days < 0 : raise ValueError ( "End date cannot be before start date." )
Validate if a date string.

    Validate if a string is a date on yyyy-mm-dd format and it the
    period between them is less than a year.