# Compiled data for DeltaT, from http://hemel.waarnemen.com/Computing/deltat.html # Values for -700 - 1600 are taken from Rob van Gent's website: http://www.phys.uu.nl/~vgent/deltat/deltat.htm, Delta T before the Telescopic Era, Table 2: Recommended values of ΔT = TT – UT (in seconds) for the period –1000 to +1700 # Values for 1620 - 1973 are taken from Rob van Gent's website: http://www.phys.uu.nl/~vgent/deltat/deltat.htm, Delta T during the Telescopic Era, Table 1: Observed values of ΔT = TT – UT1 (seconds) (values before 1955.5 based on n' = 26.0 "/cy/cy) # Values from 1974 onward are taken from ftp://maia.usno.navy.mil/ser7/deltat.data for January # Prediction for the next 1-2 years: ftp://maia.usno.navy.mil/ser7/deltat.preds # year DeltaT -700 20400 -600 18800 -500 17190 -400 15530 -300 14080 -200 12790 -100 11640 0 10580 100 9600 200 8640 300 7680 400 6700 500 5710 600 4740 700 3810 800 2960 900 2200 1000 1570 1100 1090 1200 740 1300 490 1400 320 1500 200 1600 120 1620 124 1621 119 1622 115 1623 110 1624 106 1625 102 1626 98 1627 95 1628 91 1629 88 1630 85 1631 82 1632 79 1633 77 1634 74 1635 72 1636 70 1637 67 1638 65 1639 63 1640 62 1641 60 1642 58 1643 57 1644 55 1645 54 1646 53 1647 51 1648 50 1649 49 1650 48 1651 47 1652 46 1653 45 1654 44 1655 43 1656 42 1657 41 1658 40 1659 38 1660 37 1661 36 1662 35 1663 34 1664 33 1665 32 1666 31 1667 30 1668 28 1669 27 1670 26 1671 25 1672 24 1673 23 1674 22 1675 21 1676 20 1677 19 1678 18 1679 17 1680 16 1681 15 1682 14 1683 14 1684 13 1685 12 1686 12 1687 11 1688 11 1689 10 1690 10 1691 10 1692 9 1693 9 1694 9 1695 9 1696 9 1697 9 1698 9 1699 9 1700 9 1701 9 1702 9 1703 9 1704 9 1705 9 1706 9 1707 9 1708 10 1709 10 1710 10 1711 10 1712 10 1713 10 1714 10 1715 10 1716 10 1717 11 1718 11 1719 11 1720 11 1721 11 1722 11 1723 11 1724 11 1725 11 1726 11 1727 11 1728 11 1729 11 1730 11 1731 11 1732 11 1733 11 1734 12 1735 12 1736 12 1737 12 1738 12 1739 12 1740 12 1741 12 1742 12 1743 12 1744 13 1745 13 1746 13 1747 13 1748 13 1749 13 1750 13 1751 14 1752 14 1753 14 1754 14 1755 14 1756 14 1757 14 1758 15 1759 15 1760 15 1761 15 1762 15 1763 15 1764 15 1765 16 1766 16 1767 16 1768 16 1769 16 1770 16 1771 16 1772 16 1773 16 1774 16 1775 17 1776 17 1777 17 1778 17 1779 17 1780 17 1781 17 1782 17 1783 17 1784 17 1785 17 1786 17 1787 17 1788 17 1789 17 1790 17 1791 17 1792 16 1793 16 1794 16 1795 16 1796 15 1797 15 1798 14 1799 14 1800 13.7 1801 13.4 1802 13.1 1803 12.9 1804 12.7 1805 12.6 1806 12.5 1807 12.5 1808 12.5 1809 12.5 1810 12.5 1811 12.5 1812 12.5 1813 12.5 1814 12.5 1815 12.5 1816 12.5 1817 12.4 1818 12.3 1819 12.2 1820 12.0 1821 11.7 1822 11.4 1823 11.1 1824 10.6 1825 10.2 1826 9.6 1827 9.1 1828 8.6 1829 8.0 1830 7.5 1831 7.0 1832 6.6 1833 6.3 1834 6.0 1835 5.8 1836 5.7 1837 5.6 1838 5.6 1839 5.6 1840 5.7 1841 5.8 1842 5.9 1843 6.1 1844 6.2 1845 6.3 1846 6.5 1847 6.6 1848 6.8 1849 6.9 1850 7.1 1851 7.2 1852 7.3 1853 7.4 1854 7.5 1855 7.6 1856 7.7 1857 7.7 1858 7.8 1859 7.8 1860 7.88 1861 7.82 1862 7.54 1863 6.97 1864 6.40 1865 6.02 1866 5.41 1867 4.10 1868 2.92 1869 1.82 1870 1.61 1871 0.10 1872 -1.02 1873 -1.28 1874 -2.69 1875 -3.24 1876 -3.64 1877 -4.54 1878 -4.71 1879 -5.11 1880 -5.40 1881 -5.42 1882 -5.20 1883 -5.46 1884 -5.46 1885 -5.79 1886 -5.63 1887 -5.64 1888 -5.80 1889 -5.66 1890 -5.87 1891 -6.01 1892 -6.19 1893 -6.64 1894 -6.44 1895 -6.47 1896 -6.09 1897 -5.76 1898 -4.66 1899 -3.74 1900 -2.72 1901 -1.54 1902 -0.02 1903 1.24 1904 2.64 1905 3.86 1906 5.37 1907 6.14 1908 7.75 1909 9.13 1910 10.46 1911 11.53 1912 13.36 1913 14.65 1914 16.01 1915 17.20 1916 18.24 1917 19.06 1918 20.25 1919 20.95 1920 21.16 1921 22.25 1922 22.41 1923 23.03 1924 23.49 1925 23.62 1926 23.68 1927 24.49 1928 24.34 1929 24.08 1930 24.02 1931 24.00 1932 23.87 1933 23.95 1934 23.86 1935 23.93 1936 23.73 1937 23.92 1938 23.96 1939 24.02 1940 24.33 1941 24.83 1942 25.30 1943 25.70 1944 26.24 1945 26.77 1946 27.28 1947 27.78 1948 28.25 1949 28.71 1950 29.15 1951 29.57 1952 29.97 1953 30.36 1954 30.72 1955 31.07 1956 31.35 1957 31.68 1958 32.18 1959 32.68 1960 33.15 1961 33.59 1962 34.00 1963 34.47 1964 35.03 1965 35.73 1966 36.54 1967 37.43 1968 38.29 1969 39.20 1970 40.18 1971 41.17 1972 42.23 1973 43.37 1974 44.4841 1975 45.4761 1976 46.4567 1977 47.5214 1978 48.5344 1979 49.5861 1980 50.5387 1981 51.3808 1982 52.1668 1983 52.9565 1984 53.7882 1985 54.3427 1986 54.8712 1987 55.3222 1988 55.8197 1989 56.3000 1990 56.8553 1991 57.5653 1992 58.3092 1993 59.1218 1994 59.9845 1995 60.7853 1996 61.6287 1997 62.2950 1998 62.9659 1999 63.4673 2000 63.8285 2001 64.0908 2002 64.2998 2003 64.4734 2004 64.5736 2005 64.6876 2006 64.8452 2007 65.1464 2008 65.4574 2009 65.7768 2010 66.0699 2011 66.3246 2012 66.6030 2013 66.9069 2014 67.2810 2015 67.6439 2016 68.1024 2017 68.5927 2018 68.9677 2019 69.2202 2020 69.5