The data in DeltaT.dat were taken from what appears to be the definitive
work which is Table 1 of

Title: Historical values of the Earth's clock error ΔT and the calculation
of eclipses

Authors: Morrison, L. V.; Stephenson, F. R.

Publication: Journal for the History of Astronomy (ISSN 0021-8286), Vol. 35,
Part 3, No. 120, p. 327 - 336 (2004)

Publication Date: 08/2004

The above bibliographic data and link to the paper was taken from
http://adsabs.harvard.edu/abs/2004JHA....35..327M