Dionysius Exiguus

"Dionysius Exiguus (Latin for "Dionysius the Humble",[a] Greek: Διονύσιος; c. 470 – c. 544) was a 6th-century Eastern Roman monk born in Scythia Minor. He was a member of a community of Scythian monks concentrated in Tomis (present day Constanța, Romania), the major city of Scythia Minor. Dionysius is best known as the inventor of Anno Domini (AD) dating, which is used to number the years of both the Gregorian calendar and the (Christianised) Julian calendar. Almost all churches adopted his computus for the dates of Easter."

• Wikipedia - overview of this book or author
• Archive.org - free, older, scanned, digital versions of this book or author
• eBay.com - printed, second-hand, early edition versions of this book or author
• Amazon.com - new, used, digital and print versions of this book or author

Note: The above quoted descriptions are not the words of Jason Breshears. They are collected from Wikipedia, Amazon, or wherever available. Please understand they may not represent truth.