@staticmethod
def tt2ut(year, month):
    """This method provides an approximation of the difference, in seconds,
        between Terrestrial Time and Universal Time, denoted **DeltaT**, where:
        DeltaT = TT - UT.

        Here we depart from Meeus book and use the polynomial expressions from:

        https://eclipse.gsfc.nasa.gov/LEcat5/deltatpoly.html

        Which are regarded as more elaborate and precise than Meeus'.

        Please note that, by definition, the UTC time used internally in this
        Epoch class by default is kept within 0.9 seconds from UT. Therefore,
        UTC is in itself a quite good approximation to UT, arguably better than
        some of the results provided by this method.

        :param year: Year we want to compute DeltaT for.
        :type year: int, float
        :param month: Month we want to compute DeltaT for.
        :type month: int, float

        :returns: DeltaT, in seconds
        :rtype: float

        >>> round(Epoch.tt2ut(1642, 1), 1)
        62.1
        >>> round(Epoch.tt2ut(1680, 1), 1)
        15.3
        >>> round(Epoch.tt2ut(1700, 1), 1)
        8.8
        >>> round(Epoch.tt2ut(1726, 1), 1)
        10.9
        >>> round(Epoch.tt2ut(1750, 1), 1)
        13.4
        >>> round(Epoch.tt2ut(1774, 1), 1)
        16.7
        >>> round(Epoch.tt2ut(1800, 1), 1)
        13.7
        >>> round(Epoch.tt2ut(1820, 1), 1)
        11.9
        >>> round(Epoch.tt2ut(1890, 1), 1)
        -6.1
        >>> round(Epoch.tt2ut(1928, 2), 1)
        24.2
        >>> round(Epoch.tt2ut(1977, 2), 1)
        47.7
        >>> round(Epoch.tt2ut(1998, 1), 1)
        63.0
        >>> round(Epoch.tt2ut(2015, 7), 1)
        69.3
        """
    y = year + (month - 0.5) / 12.0
    if year < -500:
        u = (year - 1820.0) / 100.0
        dt = -20.0 + 32.0 * u * u
    elif year >= -500 and year < 500:
        u = y / 100.0
        dt = 10583.6 + u * (-1014.41 + u * (33.78311 + u * (-5.952053 + u *
            (-0.1798452 + u * (0.022174192 + 0.0090316521 * u)))))
    elif year >= 500 and year < 1600:
        dt = 1574.2 + u * (-556.01 + u * (71.23472 + u * (0.319781 + u * (-
            0.8503463 + u * (-0.005050998 + 0.0083572073 * u)))))
    elif year >= 1600 and year < 1700:
        t = y - 1600.0
        dt = 120.0 + t * (-0.9808 + t * (-0.01532 + t / 7129.0))
    elif year >= 1700 and year < 1800:
        t = y - 1700.0
        dt = 8.83 + t * (0.1603 + t * (-0.0059285 + t * (0.00013336 - t / 
            1174000.0)))
    elif year >= 1800 and year < 1860:
        t = y - 1800.0
        dt = 13.72 + t * (-0.332447 + t * (0.0068612 + t * (0.0041116 + t *
            (-0.00037436 + t * (1.21272e-05 + t * (-1.699e-07 + 8.75e-10 *
            t))))))
    elif year >= 1860 and year < 1900:
        t = y - 1860.0
        dt = 7.62 + t * (0.5737 + t * (-0.251754 + t * (0.01680668 + t * (-
            0.0004473624 + t / 233174.0))))
    elif year >= 1900 and year < 1920:
        t = y - 1900.0
        dt = -2.79 + t * (1.494119 + t * (-0.0598939 + t * (0.0061966 - 
            0.000197 * t)))
    elif year >= 1920 and year < 1941:
        t = y - 1920.0
        dt = 21.2 + t * (0.84493 + t * (-0.0761 + 0.0020936 * t))
    elif year >= 1941 and year < 1961:
        t = y - 1950.0
        dt = 29.07 + t * (0.407 + t * (-1.0 / 233.0 + t / 2547.0))
    elif year >= 1961 and year < 1986:
        t = y - 1975.0
        dt = 45.45 + t * (1.067 + t * (-1.0 / 260.0 - t / 718.0))
    elif year >= 1986 and year < 2005:
        t = y - 2000.0
        dt = 63.86 + t * (0.3345 + t * (-0.060374 + t * (0.0017275 + t * (
            0.000651814 + 2.373599e-05 * t))))
    elif year >= 2005 and year < 2050:
        t = y - 2000.0
        dt = 62.92 + t * (0.32217 + 0.005589 * t)
    elif year >= 2050 and year < 2150:
        dt = -20.0 + 32.0 * ((y - 1820.0) / 100.0) ** 2 - 0.5628 * (2150.0 - y)
    else:
        u = (year - 1820.0) / 100.0
        dt = -20.0 + 32.0 * u * u
    return dt
