Because python doesn't support negative timestamp to datetime
    so we have to implement my own method

def fromtimestamp(timestamp):
    """Because python doesn't support negative timestamp to datetime
    so we have to implement my own method
    """
    if timestamp >= 0:
        return datetime.fromtimestamp(timestamp)
    else:
        return datetime(1969, 12, 31, 20, 0) + timedelta(seconds=timestamp)