def millis_offset_between_epochs(reference_epoch, target_epoch):
    """
    Calculates the signed milliseconds delta between the reference unix epoch and the provided target unix epoch
    :param reference_epoch: the unix epoch that the millis offset has to be calculated with respect to
    :type reference_epoch: int
    :param target_epoch: the unix epoch for which the millis offset has to be calculated
    :type target_epoch: int
    :return: int
    """
    assert isinstance(reference_epoch, int)
    assert isinstance(target_epoch, int)
    return (target_epoch - reference_epoch)*1000