import time


def convert_millisecond_date(x: int, date_format: str = "%Y-%m-%d") -> str:
    """
    Converts a date in milliseconds to a string date.

    :param x: time in milliseconds
    :param date_format: date format to return
    :return: time in date format
    """
    return time.strftime(date_format, time.gmtime(x / 1000.0))