Empirical transformations from U.T. to E.T. for the period 1800–1988 (Astronomisches Rechen-Institut — Mitteilungen Serie B)

Approximation formulae describing the long-term changes in the rotation of the Earth are evaluated. The time scale reduction from Universal to Ephemeris Time can be accomplished by a 12th degree polynomial with a mean error of less than one second for the entire time span 1800–1988. The maximum residuals of least squares fits of the 19th and 20th century data, respectively, can be limited to this accuracy by even simpler expressions.