Dates are obviously really important when talking about history, but there’s a few small details that can make it a bit confusing. So today I want to explain all the little letter next to those numbers. There’s a number of different calendars out there, but the one most commonly used internationally, and the one you’ll find yourself having to memorize in class, is the Gregorian calendar. The Gregorian calendar is also called the Western calendar and the Christian calendar. It’s named after Pope Gregory XIII, who introduced it in 1582. What’s the difference between CE/BCE or AD/BC dating notation? Because it’s pretty hard to agree on when time started, Christian decided to count years using Jesus Christ’s birth as a reference point. Years before Christ’s birth counts backwards, and is noted with BC, which stands for “Before Christ”. AD is used to note years after Christ’s birth - AD 1 is the year Christ was born. And no, A.D doesn’t stand for “After Death”, but actually Anno Domini, Latin for "In the year of our Lord.” So going from older to newer, it would be 2 BC, 1 BC, then AD 1 (when Chirst is born; there is no year 0), then AD 2, and so on. For example, 500 BC, which is 500 years before Christ’s birth, is older than 10 BC, 10 years before Christ's birth. Whereas, AD 500 is more recent than AD 10. Today, a more common notation you’ll see in any newer text is BCE and CE instead of BC and AD. These are actually using the same calendar system - counting years in relation to Christ’s birth - so the years are exactly the same way, but the abbreviations are simply changed to “Before Common Era” and “Common Era.” 50 BC refers to the same year as 50 BCE, and AD 2015 is the same as 2015 CE. Now you probably noticed that I’ve been saying AD before the year, whereas BC, BCE and CE follow the year. If there’s no notation, then it is AD or CE, like you know 2015 refers to this year, the year this video was made, but you should always use BC or BCE to avoid confusion. Whether you use BC/AD or BCE/CE, just stick with it throughout your essay or article. Just don’t change any direct quotes. What is c., ca., and circa? That is an abbreviation of the Latin word “circa” meaning approximately. A lot of times we don’t know the exact date an object was made, so experts do their best to pinpoint an approximate date and use circa to say that it’s somewhere around there. If the c. is after the number, then it is referring to the century. ex. 15 c. is the fifteenth century. Centuries and Millennias Currently, in the year 2015, we are living in the 21st century. Why not the 20th century? How to calculate centuries? Well, a century is a hundred years, pretty straight forward, and the first century CE (aka AD) refers to January 1, 1 CE through December 31, 100 CE. So January 1, 101 CE is part of the 2nd century CE, ending on December 31, 200 CE. So always remember century is that number including 100 years before that number, not after. The same can be applied to the use of millennias. A millennium equals 1000 years. Currently we’re living in the third millennium CE, which started in January 1, 2001, and will continue until December 31, 3000. So remember December 31, 1999, when everyone was freaking out that it was the end of the millenium? Well, they were a year early!