def calc_angle(main_vector, second_vector):
    """
    Calculate angle between two vectors

    :param main_vector: DB.XYZ
    :param second_vector: DB.XYZ
    :return: Angle with sign
    :rtype: float
    """
    angle = main_vector.AngleTo(second_vector)
    sign = 1 if main_vector.CrossProduct(second_vector).Z >= 0 else -1
    return sign * angle