(My latest book God vs. Darwin: The War Between Evolution and Creationism in the Classroom has just been released and is now available through the usual outlets. You can order it from Amazon, Barnes and Noble, the publishers Rowman & Littlefield, and also through your local bookstores. For more on the book, see here.)

Bishop James Ussher arrived at his creation year of 4004 BCE by going backwards, starting by first fixing the date of the earliest event in the Bible that could be corroborated with other historical sources. This occurred after the capture and taking into exile of king Jehoiachin of Judah by Babylonian king Nebuchadnezzar in 597 BCE. The death of Nebuchadnezzar in 562 BCE (the date of which was known from other sources) is reported in the Bible to have coincided with the 37th year of exile of Jehoiachin, as stated in the Bible in 2 Kings 25:27. (Note that the dates are sometimes off by a year or two because of the differences in the calendars in use at that time.)

From that fixed reference point he worked backwards using the Bible alone, first by adding up the years that the successive kings ruled the divided kingdoms, the southern one of Judah and the northern one of Israel, and then going further back using the famous ‘begats’ in the Bible which gives a genealogy that goes back to Adam. For example, Genesis 5 gives the chronology from Adam to Noah, and then after a lot of stuff about the flood, Genesis 11 gives the genealogy from Noah to Abraham.

It is interesting that in addition to saying how long each person lived, it gives the crucial information as to the age of the person when his eldest son was born, without which Ussher’s calculation cannot be done. I am intrigued as to why the authors of the Bible put in that gratuitous piece of extra information, which is not an obvious thing to do, unless they wanted to create a timeline.

It is interesting that from Adam to Abraham, there is an unbroken line of males. The youngest age at which any of them had their first son was 65 but Noah is the clear record holder for the oldest father, his oldest son being born when he was 500! The oldest man ever was Methuselah who lived to the age of 969, though he had his first son when he was a mere child of 187. Oddly enough, after Noah, although the men still lived for hundreds of years, the age at which they became fathers for the first time drops suddenly to the early thirties, until it gets to the father of Abraham who was 70.

Although the genealogies say that sons and daughters were born, only males are named. As far as I can tell, after Eve, all the women who are born are nameless until we get to Sarah, Abraham’s wife, about 1,800 years later.

Ussher’s choice of the Hebrew Bible to obtain his chronology may have been influenced by the fact that this particular Bible gives a nice round date of 4000 BCE for the year of creation. The then current belief was that the world would last only 6,000 years, this being the interpretation of the six days of creation in Genesis combined with the statement in Psalms 90: 4 that “For a thousand years in your sight are like a day that has just gone by, or like a watch in the night” and the New Testament statement (2 Peter 3:8) that “With the Lord a day is like a thousand years, and a thousand years are like a day.” Thus according to his chronology, Jesus was born 4,000 years after the creation and the world would end in 2,000 CE (also called the Anno Domini or AD calendar), which provided a nice symmetry, no doubt showing that god was a careful planner.

However, that rounding of dates had to be adjusted because the creator of the CE calendar had made a mistake. When corrected, it was noted that King Herod had begun his reign in 37 BCE and died in 4 BCE, so Jesus had to have been born sometime during that period because the New Testament says Jesus was born during Herod’s reign. Ussher fixed Jesus’s birth year as 4 BCE and this required the shifting of all the dates by 4 years, moving the year of creation to 4004 BCE.

Wikipedia has an summary of how Ussher managed to pin point the very day when god created the world.

The season in which Creation occurred was the subject of considerable theological debate in Ussher’s time. Many scholars proposed it had taken place in the spring, the start of the Babylonian, Chaldean and other cultures’ chronologies. Others, including Ussher, thought it more likely that it had occurred in the autumn, largely because that season marked the beginning of the Jewish year.

Ussher further narrowed down the date by using the Jewish calendar to establish Creation as beginning on a Sunday near the autumnal equinox. The day of the week was a backward calculation from the six days of creation with God resting on the seventh, which in the Jewish tradition is Saturday — hence Creation began on a Sunday. The astronomical tables that Ussher probably used were Kepler’s Tabulae Rudolphinae (Rudolphine Tables, 1627). Using them, he would have concluded that the equinox occurred on Tuesday October 25, only one day earlier than the traditional day of its creation, on the fourth day of Creation week, Wednesday, along with the Sun, Moon, and stars (Genesis 1:16). Modern equations place the autumnal equinox of 4004 BC on Sunday October 23.

Ussher stated his time of Creation (nightfall preceding October 23) on the first page of Annales in Latin and on the first page of its English translation Annals of the World (1658).

You can read the first page of his book (a revised edition with the English updated to be easily intelligible to the modern reader) here. Sometimes one hears that he fixed the time of creation as 9:00 am but that claim was made by someone else before Ussher and has been mistakenly attributed to him.

I have to admit that I kind of like Ussher’s calculations. The fact that it is totally wrong and that to take it seriously now is to live in an alternative reality does not diminish his achievement.

POST SCRIPT: How to choose your religion

Looking for a religion but not sure which to pick from the wide variety of choices? GrrlScientist has put together a nifty little flowchart to help you out. (via Pharyngula)