Common Era or Current Era, abbreviated CE, is a calendar era that is often used as an alternative naming of the Anno Domini system ("in the year of the Lord"), abbreviated AD. The system uses BCE as an abbreviation for "before the Common (or Current) Era" and CE as an abbreviation for "Common Era". The CE/BCE designation uses the year-numbering system introduced by the 6th-century Christian monk Dionysius Exiguus, who started the Anno Domini designation, intending the beginning of the life of Jesus to be the reference date. Neither notation includes a year zero, and the two notations (CE/BCE and AD/BC) are numerically equivalent; thus " CE" corresponds to "AD ", and "400 BCE" corresponds to "400 BC". The Gregorian calendar and the year-numbering system associated with it is the calendar system with most widespread use in the world today. For decades, it has been the global standard, recognized by international institutions such as the United Nations and the Universal Postal Union.