Convert a date, or datetime to unix timestamp
    :param value:
    :return:

def unix(value):
    """
    Convert a date, or datetime to unix timestamp
    :param value:
    :return:
    """
    if isinstance(value, (date, builtin_datetime)):
        pass
    elif value < 10000000000:
        value = unix2datetime(value)
    else:
        value = milli2datetime(value)

    return str(datetime2unix(value))