4004 BC The world is created
The notion that the universe is not very old found its greatest expositor in James Ussher, the Archbishop of Armagh. His study of history led him to publish in 1650 the highly influential 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.”) According to Ussher God created Earth on 23 October 4004 BC (it was a Saturday, around nightfall.)
Estimating the age of the world and creating a universal chronology using the Bible had occupied any number of Jewish and Christian scholars — even Isaac Newton had given it a try. There was a general consensus that the world had been created around 4,000 years before the birth of Christ: Johannes Kepler had placed the date as 3992 BC, the Venerable Bede thought it was 3952 BC, and Jose ben Halafta pegged it at 3761 BC. The trick was to use the genealogies in the Old Testament, which were explicit up to the reign of Solomon, and extrapolate from that point tying Biblical events to the reliable dates of occurrences in other cultures. Then there were astronomical calculations to pin down the date of the equinoxes and adjustments with the Jewish calendar. Then he had to fudge a little on the date of Christ’s birth, placing it at 5 BC. The results were artistically satisfying — the building of Solomon’s Temple could be placed exactly 3,000 years after Creation and 1,000 before the birth of Jesus.
Ussher’s ideas were highly influential and were taken seriously until the 19th century when geological observations began to argue for a much older universe.