" Bishop James Ussher was able to use the ages of famous pre-flood personages in the Bible to estimate the number of years between creation and the flood. In 1650 CE, he published his book "Annales veteris testamenti, a prima mundi origine deducti" ("Annals of the Old Testament, deduced from the first origins of the world.") He calculated that God had created the Earth in 4004 BCE. A decade earlier, Dr. John Lightfoot, (1602 - 1675), an Anglican clergyman, rabbinical scholar, and Vice-Chancellor of the University of Cambridge had already arrived at an estimate of 4004-OCT-23 BCE, at 9 AM. (We assume that this was either Greenwich Mean Time (GMT) or Jerusalem time)."
Crazy people tried to figure out the "creation date" of the earth for a long time- but by the 20th century only Franz and a few other loons still believed that- since geology had proven that the earth was 4.5 Billion years old. (I crack up at the 9AM thing!!)