The Ussher chronology is a 17th-century chronology of the history of the world formulated from a literal reading of the Old Testament by James Ussher, the Archbishop of Armagh and Primate of All Ireland. The chronology is sometimes associated with young Earth creationism, which holds that the universe was created only a few millennia ago by God as described in the first two chapters of the biblical book of Genesis. Ussher's work fell into disrepute in the 19th century.
Published in 1650, the full title of Ussher's work in Latin is Annales Veteris Testamenti, a prima mundi origine deducti, una cum rerum Asiaticarum et Aegyptiacarum chronico, a temporis historici principio usque ad Maccabaicorum initia producto ("Annals of the Old Testament, deduced from the first origins of the world, the chronicle of Asiatic and Egyptian matters together produced from the beginning of historical time up to the beginnings of Maccabees").
Ussher's work was his contribution to the long-running theological debate on the age of the Earth. This was a major concern of many Christian scholars over the centuries.
The chronology is sometimes called the UssherLightfoot chronology because John Lightfoot published a similar chronology in 1642–1644. This, however, is a misnomer, as the chronology is based on Ussher's work alone and not that of Lightfoot. Ussher deduced that the first day of creation was October 22, 4004 BC on the proleptic Julian calendar, near the autumnal equinox. Lightfoot similarly deduced that Creation began at nightfall near the autumnal equinox, but in the year 3929 BC.
Ussher's proposed date of 4004 BC differed little from other biblically based estimates, such as those of Jose ben Halafta (3761 BC), Bede (3952 BC), Ussher's near-contemporary Scaliger (3949 BC), Johannes Kepler (3992 BC) or Sir Isaac Newton (c. 4000 BC). Ussher was influenced by the same account as the apocryphal Book of Jasher, dating the worldwide flood to 2349 BC and the birth of Terah in 2127 BC.