If You're Confused About Dates in History, Here's the Explanation

                                                                   

Jewish calendar with sun as used in it, synchronizing with solar calendar

                                                                         

The Jewish Calendar uses the Moon to mark time.  It is a lunar calendar.

Nadene Goldfoot
2000 BCE  1500 BCE 1391 BCE 1271 BCE 1000 BCE, 500 BCE  0 100 CE 500 CE 1000   2015
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BCE means Before the Common Era.  That is referring to the time of Jesus of the Christian religion.
BCE is used by Jews because BC refers to Before Christ, and Christ is somebody we do not accept in our faith.  Therefore, Gentiles use only BC and AD.  AD refers to the Roman phrase, Anno Domini, or After Christ.
Jews use CE, meaning:  The Common Era.

Notice in the BCE era the numbers grow smaller until they reach 0.  Then they grow larger.
54321  0  12345
                                                                     

The Biblical era for Jews started with Abraham who was born in the 2nd millennium BCE.  We figure it was in the year 1948 BCE.  So the history of our religion is about 4,000 years old.  We consider Abraham the father of Judaism.  He was the first monotheist, believing in one unseen G-d.  It was a shocking revelation for other people had to have something they could see, like idols and statues, rocks, anything.

It's hard to understand, but there have been people just like us for the past 25,000 years or longer.  The biblical era is fairly new.  We humans are homo-sapiens.  There were also Neanderthals in Europe at the time when homo sapiens existed.  "Genetic studies now suggest that the functional DNA of modern humans and Neanderthals diverged 500,000 years ago.  So we can say that we have existed as far back in human form as 500,000 years ago.  The forces of natural selection have continued to operate on human populations, with evidence that certain regions of the genome display directional selection in the past 15,000 years."  

Take the line from Moses and his brother, Aaron.  They would have had the Y haplogroup of J1, which is called the Cohen gene, named for the assignment Moses gave to Aaron as high priest or Cohen.  It was a line handed down from father to son.  Thus, we find  Cohens of today also with J1 haplogroup.  "This haplogroup is found to have arisen 10,000 to 15,000 years ago in the Fertile Crescent, and Abraham was born only about 4,000 years ago."  
                                                                                                                

A Jewish year and its holidays in its 12 months

The Jewish calendar follows the movements of the moon.  Today's date in international dating is 2015.  On the Jewish calendar it is the year 5776.  It started back in the BCE dating period.  It also is made up of 12 months but calculated according to the moon.  The difference between the lunar years of 354 days and the solar (sun) year of 365.25 days is made up by adding a full month after the month of Adar in the 3rd, 6th, 8th, 11th, 14th and 17th and 19th year of each 19-year cycle .  The year 5749 began such a cycle.  The month so added is called Adar Sheni or the 2nd Adar, and the year becomes a leap year.  

The calendar that is used internationally is a solar calendar.  It is called a Gregorian calendar.  "The first calendar reform of the early modern era was the Gregorian calendar, introduced in 1582 based on the observation of a long-term shift between the Julian calendar and the solar year.  
                                                                 

The Kabba, Mecca, Saudi Arabia where it is say by Islamists a place that dates back to Abraham.  

 "The Islamic calendar or Hijri calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in most of the Muslim countries (concurrently with the Gregorian calendar), and used by Muslims everywhere to determine the proper day on which to celebrate Islamic holy days and festivals. Its epoch is the Hijra (corresponding to year 622 of the Dionysian era). With an annual drift of 11 or 12 days, the seasonal relation is repeated approximately each 33 Islamic years."

The Islamic calendar "The Islamic calendar is based on the prohibition of intercalation (nasi') by Muhammad, in Islamic tradition dated to a sermon held on 9 Dhu al-Hijjah AH 10 (Julian date: 6 March 632). This resulted in an observationally based lunar calendar shifting relative to the seasons of the solar year.  Notice it started after 632 when Muhammad died, so it is a very recent calendar. "Years are counted since the Hijra, that is, Mohammed's emigration to Medina in AD 622. On 16 July (Julian calendar) of that year, AH 1 started (AH = Anno Hegirae = year of the Hijra). In the year AD 2003 Muslims  have witnessed the start of Islamic year AH 1424.

2015=5776=1424.  This year.  

Reference:  https://en.wikipedia.org/wiki/Homo_sapiens
http://jewishfactsfromportland.blogspot.com/2010/01/jewish-genes-what-haplogroup-could-they.html
http://www.stevemorse.org/hebrewcalendar/hebrewcalendar.htm
http://www.webexhibits.org/calendars/calendar-islamic.html