import time


def format_time(epoch, format="%m/%d %H:%M", default="--/-- --:--"):
    """Formats time using time formatting standards.

    See: https://docs.python.org/3/library/time.html

    :type  epoch: int
    :param epoch: time as an epoch
    :type  format: str
    :param format: desired format of output string
    :type  default: str
    :param default: the output if the given time is empty
    :rtype: str
    :return: string-formatted version of the given time
    """
    if not epoch:
        return default
    return time.strftime(format, time.localtime(epoch))