The second millennium of the Anno Domini or Common Era was a millennium spanning the years 1001 to 2000. It began on January 1, 1001 (MI) and ended on December 31, 2000 (MM), (11th to 20th centuries; in astronomy: JD2086667.5 – 2451909.5[1]).
World population grew without precedent over the millennium, from about 310 million in 1000 to about 6 billion in 2000. The population growth rate increased dramatically during this time; world population approximately doubled to 600 million by 1700, and doubled more than three more times by 2000, ultimately reaching about 1.8% per year in the second half of the 20th century.
The Julian calendar was used in Europe at the beginning of the millennium, and all countries that once used the Julian calendar had adopted the Gregorian calendar by the end of it. For this reason, the end date of the 2nd millennium is usually calculated based on the Gregorian calendar, while the beginning date is based on the Julian calendar (or occasionally the proleptic Gregorian calendar).
In the late 1990s, there was a dispute as to whether the millennium should be taken to end on December 31, 1999, or December 31, 2000.
Stephen Jay Gould at the time argued there is no objective way of deciding this question.[4]Associated Press reported that the third millennium began on 1 January 2001, but also reported that celebrations in the US were generally more subdued at the beginning of 2001, compared to the beginning of 2000.[5]
Many public celebrations for the end of the second millennium were held on December 31, 1999 – January 1, 2000[6]—with a few people marking the end of the millennium a year later.
