The designation of time that refers to the dates before the birth of Christ using the year-numbering system of the Gregorian calendar. This was formerly shown as BC or the abbreviation for before Christ. Before the Common Era is almost always seen as in its abbreviated form, BCE. The term Before the Common Era and before Christ have the same value, so the year 500 BCE refers to the same year as 500 BC. Both systems start with the year "1" and neither uses the year "zero". Before the Common Era has also been referred to as "Before the Christian Era" or "Before the Current Era".
The former designation of AD (Anno Domini Latin for "the year of the Lord") is now shown as CE or Common Era.