|Jewish Calendar: Numbering of Jewish Years
The year number on the Jewish calendar represents the number of years since creation, calculated by adding up the ages of people in the Bible back to the time of creation. However, this does not necessarily mean that the universe has existed for only 5600 years as we understand years. Many Orthodox Jews will readily acknowledge that the first six "days" of creation are not necessarily 24-hour days (indeed, a 24-hour day would be meaningless until the creation of the sun on the fourth "day").
For a fascinating (albeit somewhat defensive) article by a nuclear physicist showing how Einstein's Theory of Relativity sheds light on the correspondence between the Torah's age of the universe and the age ascertained by science.
Jews do not generally use the words "A.D." and "B.C." to refer to the years on the Gregorian calendar. "A.D." means "the year of our L-rd," and we do not believe Jesus is the L-rd. Instead, we use the abbreviations C.E. (Common or Christian Era) and B.C.E. (Before the Common Era).
The Age of Universe
One of the most obvious perceived contradictions between Torah and science is the age of the universe. Is it billions of years old, like scientific data, or is it thousands of years, like Biblical data? When we add up the generations of the Bible, we come to 5700-plus years. Whereas, data from the Hubbell telescope or from the land based telescopes in Hawaii, indicate the number at 15 billion years.
In trying to resolve this apparent conflict, it's interesting to look historically at trends in knowledge, because absolute proofs are not forthcoming. But what is available is to look at how science has changed its picture of the world, relative to the unchanging picture of the Torah. Because the Torah doesn't have the option of changing. (I refuse to use modern Biblical commentary, because modern commentary already knows modern science, and so it is influenced by that always.)
So the only data I use as far as Biblical commentary goes is ancient commentary. That means the text of the Bible itself (3300 years ago), the translation of the Torah into Aramaic by Onkelos (100 CE), the Talmud (redacted about the year 500 CE), and the three major Torah commentators. There are many, many commentators, but at the top of the mountain there are three, accepted by all: Rashi (11th century France), who brings the straight understanding of the text, Maimonides (12th century Egypt), who handles the philosophical concepts, and then Nachmanides (13th century Spain), the earliest of the Kabbalists.
This ancient commentary was finalized hundreds or thousands of years ago, long before Hubbell was a gleam in his great-grandparent's eye. So there's no possibility of Hubbell or any other scientific data influencing these concepts. That's a key component in my attempt to keep the following discussion objective.