THE 2nd MILLENNIUM

The 2nd millennium was the thousand-year period that commenced on January 1, 1001 and ended on December 31, 2000, encompasses the High Middle Ages, the Renaissance, the Early Modern Age, the age of Colonialism, industrialization, the rise of nation states, and culminates in the 20th century with the impact of science, widespread education, and universal health care and vaccinations in many nations. The centuries of expanding large-scale warfare with high-tech weaponry (of the World Wars and nuclear bombs) were offset by growing peace movements from the United Nations, the Peace Corps, religious campaigns warning against violence, plus doctors and health workers crossing borders to treat injuries and disease and the return of the Olympics as contest without combat.
Scientists prevailed in explaining intellectual freedom; humans took their first steps on the Moon during the 20th century; and new technology was developed by governments, industry, and academia across the world, with education shared by many international conferences and journals. The development of movable type, radio, television, and the Internet spread information worldwide, within minutes, in audio, video, and print-image format to educate, entertain, and alert billions of people by the end of the 20th century.
From the 16th century, humans migrated from Europe, Africa and Asia to, what was to them, the New World, beginning the ever-accelerating process of globalization. The interwoven international trade led to the formation of multi-national corporations, with home offices in multiple countries. International business ventures reduced the impact of nationalism in popular thought.
The world population doubled over the first seven centuries of the millennium, (from 310 million in AD 1000 to 600 million in AD 1700), and later increased tenfold over its last three centuries, exceeding to 6 billion in AD 2000.

The 2nd millennium was a period of time that commenced on January 1, 1001, and ended on December 31, 2000. This is the second period of one thousand years Anno Domini.
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. So the end date is always calculated according to the Gregorian calendar, but the beginning date is usually according to the Julian calendar (or occasionally the Proleptic Gregorian calendar).
The current millennium is perhaps more popularly (albeit inaccurately) thought of as beginning and ending a year earlier, thus starting at the beginning of 1000 and finishing at the end of 1999. Many public celebrations for the end of the millennium were held on December 31, 1999–January 1, 2000—with few on the actual date a year later. The inaccuracy stems from the assumption that there is a year zero, however this is not the case for this calendar.