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New Millennium is When?

Many people might wonder why the first day of the next millennium is January 1, 2001, not January 1, 2000. A millennium is a period of 1000 years. The calendar of the western world is based on the Julian calendar, which dates back to the time of Julius Caesar (44 BC). In what is now referred to as the sixth century, Dionysius Exiguus codified what was already popular belief by designating "AD 1" (anno domini) as the year of Christ's birth 532 years earlier. When endorsed by the Venerable Bede two centuries later, the method of reckoning the past as BC and AD was formally adopted. Since the system had no year "0", 1 BC was followed directly by 1 AD. Therefore, the 1000th year was completed on December 31, 1000, and the second millennium began on January 1, 1001. Accordingly, January 1, 2001, will be the first day of the third millennium.

Not convinced? Lets look at the first decade.

Note the first year is one not zero. Normal methods of counting have the concept of a zero value. Our children are not one year old until their first birthday; you could say they are zero years old before their first birthday.
When the calendar was organized by Dionysius Exiguus, the year zero was not defined. Thus the whole calendar is shifted by one. So the first decade includes the year 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. The second decade starts at the beginning of year 11.

Now let's see what happens in 2000.

Because of the missing year zero, the second Millennium includes the year 2000 just like the first decade includes the year 10..

Much could be argued that the second Millennium should be redefined to not include the year 2000. It is beyond the scope of this article to make any declarations. Hey, at least we have two new year's occasions to celebrate: One is the end of the 90's and the following year the end of the second Millennium.

References:

• USNO Millennium Program
• USNO Countdown Clock

Related Resources:

• http://www.calendarzone.com/
• http://astro.nmsu.edu/~lhuber/leaphist.html

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