If you’re a devout Christian, it’s pretty clear; heaven and hell begin with the birth of Christ. This is year one. Time begins here. Everything before is Before Christ, B.C. everything after is after or A.D. in the year of our Lord. If you’re a physicist, it isn’t quite so simple. Albert Einstein in particular got the concept of time wrapped up with long thoughts on cosmic concepts of space, dimension and relativity. He didn’t spend much time worrying about whether time was A.D. or B.C.
The ancient Romans were as clear as the Christians on how time could be be measured and understood. Time began with the founding of Rome (around 732, B.C.) and the years were marked by the annual election of the consuls. One of the perks of a successful consular election was you got the year named after you and your co-consul. For example, the advocate Cicero and his co-consul had their year named after them. This system was in place for more than a thousand years. Made perfect sense if you were a Roman. Rome ruled the world. Time started with Rome.
The final details of the Roman calendar were worked by Sosigenes, an Alexandrian astronomer. His work was quite accurate losing only 11.5 minutes on the solar year per year. Julius Caesar liked his work, reformed the old Roman calendar and the new system was named after him – the Julian calendar.
This way of measuring the passage of time was used by the British until 1751 and the Russians until 1918. Non Roman Catholic, nations tended to resist the Gregorian reform introduced by Pope Gregory in 1582 although it was just a refinement of the Julian, bring more accurate by losing only about 26 seconds a year.
The Muslim world uses the lunar calendar which is whole different cycle from the solar. You need to be a much better mathematician to figure it out because the lunar cycle varies more vigorously than the solar.
If you take Einstein’s thought that time bends as correct, it makes sense to pick an arbitrary starting point to begin the measuring of human time as cosmic time probably has no starting point. Hence, the B.C./A.D. arbitrary beginning is as good as anything, but not being a devout Christian, it’s never made sense to me that the birth of the founder of any particular religion should be that arbitrary point for all of humanity. If I had to pick an arbitrary starting point for measuring human time, I would pick for the invention of writing which is marked by writing of the the epic poem Gilgamesh, 2750, B.C. in the Akkadian language.
Gilgamesh is the first record of writing that we have. It is from the Sumerian city of Uruk in present day Irak. Before the invention of writing in Uruk, which spread very quickly to other cities and other places, humanity had no way of recording the passage of time in human terms. It was all seasonal, the year of the flood, at the full moon and so on. Hence, it can be argued successfully until Gilgamesh came along, there was no time measured in human terms.
Gilgamesh is a complex and beautiful epic poem from which many of humanity’s great narratives are drawn. It was also written at the very beginning of the greatest revolution humanity will ever experience – the urban revolution.
Gilgamesh precedes the Bible, Homer and the Koran by thousands of years and it is secular which is to say it is common to all peoples and all nations. And it marks humanity’s most important invention, writing without which very little else would have been possible including the internet.
So my vote for measuring human time is an urban one. It’s B.G and A.G. Before Gilgamesh and After Gilgamesh.