Long-term Delta T
Monthly determinations and long-term predictions of Delta T from finals.data are provided (ASCII). Historic Delta T and LOD are also provided (ASCII). Terrestrial Time (TT) is defined here
Monthly values of (TT - UT1) since 1973. Updated quarterly.
Predictions of (TT - UT1) from the present tthrough 2027. Updated annually.
Plots of historic Delta T and historic length-of-day (LOD) are shown below. Error bars are indicated in white. Data points are shown in red.