Also, years have often been organized into eras, with each era providing a new “cycle.” Our own era—the Christian (or Common) Era—was the creation of a sixth-century A.D. Syrian monk named Dionysius Exiguus, who borrowed the idea from the Seleucids, the Hellenistic rulers of much of the Near East following the death of Alexander in 323 B.C. (see the following Origins columns in Archaeology Odyssey: William H. Hallo, “In One Era and Out the Other,” Premiere Issue 1998; and Leonora Neville, “Fixing the Millennium,” January/February 2000).


Although the year is common to cultures around the world, ancient and modern, it is sometimes defined differently. For example, the lunar year is defined by the cycles of the moon, rather than by the earth’s orbit around the sun. Some lunar calendars make use of intercalation (the adding of days or months) to reorient the lunar year to the solar year. But the Islamic lunar calendar does not, meaning that every successive new year begins on a different day of the solar year.


The name “January” was chosen to honor Janus, a two-headed god who looked both toward the past and toward the future.