Dates in secular history become more certain with the founding of the Medo-Persian Empire.
One of Ussher’s many projects was to write a complete history of the world in Latin, covering every major event from the time of creation to AD 70. An English translation entitled was first published in 1658, two years after his death. It has recently been translated into modern English and republished.1) In preparing this work, Ussher first made the assumption that the Bible is the only reliable source of chronological information for the time periods covered therein.
In fact, before the Persian Empire (approximately the sixth to third centuries BC) very little is known from any source about Greek, Roman and Egyptian history or the history of other nations; much rests on speculation and myths.
However, when the Gregorian calendar corrections are applied to the Julian date of October 23, 4004 BC, we get the Gregorian date September 21, 4004 BC, which is the normal day for the autumnal equinox.
Is there any way that we can verify Ussher’s date for creation?
The age of the earth is one of the most contentious issues in the creation/evolution debate.