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The third millennium is the third period of one thousand years in the Common Era. However, there are two opinions on the start and end dates.
For those who start counting their calendar from January 1 1, then the third millennium began on January 1, 2001 and will end on December 31, 3000 in the sense of the Gregorian calendar.
In the sense of the Common Era calendar the third millennium began on January 1, 2000 and will end on December 31, 2999 . The majority of the celebrations for the start of the third millennium occurred at midnight on December 31 1999 / January 1 2000. The first decade of the new millennium (see below) contains the year 2000.
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