How did they know to count the years before Christ, as they had no idea of when he was coming?
History of the AD/BC notation:
"The AD/BC notation was first proposed by the monk Dionysius Exiguus (Dennis the Little) in the year 525 CE. He used it to identify the years in the Easter tables that he prepared. He did not use the notation to date historical events. "Dionysius implied, but never stated, that Jesus was born 25 December 1 BC." 1 The basis on which he linked the divide between BC and AD to the birth of Jesus is unknown. There is general agreement that he guessed incorrectly."
There is more to this at:
There has always been yesterday, today and tomorrow. Tomorrow never comes, yesterday has been and gone so that only leaves today. Enjoy!!!!!!!!!!!!
The ancient Hewbres had their own calendar that did not rely on BC/AD.
For example, Hebrew year 5770 began on 19 September 2009 and ended on 8 September 2010.