The century known as the twenty-first century comprises the years 2001-2100. This is different from the century known as the twenty hundreds, which comprises the years 2000-2099. These were preceded by centuries known as the twentieth century (1901-2000) and the nineteen hundreds (1900-1999), respectively.
These two systems are often confused, because "century" means a hundred-year period, but the two systems start their centuries on different years. Use of the former system is more common among historians ("the U.S. civil war was in the nineteenth century"). Use of the latter is more common among the general public ("the U.S. civil war was in the eighteen hundreds").
The twenty-first century is the first century of the third millennium (2001-3000). The twenty hundreds is the first century of a millennium which could be called the two thousands (2000-2999). But the first decade of this century (2000-2009) is also often called that.
The increasing prevalence of global communications and encounters with other calendars (Islamic calendar, Chinese calendar, Persian calendar, Hebrew calendar) suggest that the terms "21st century" and "the third millennium" has a substantial cultural bias. Some futurists suggest simply abandoning the idea of "centuries", setting the start date back to the beginning of human urbanization in the 4th millennium BC, making this the Seventh Millennium. Within that, some suggest also adopting a cyclic time[?] model based on global climate change, which they view as the macro-equivalent of the annual seasons.
Predictions for the 21st century as of 2003 Please note that these predictions are controversial, and disputed by many other observers: they are listed here to show some late 20th century futurists' predictions of the events of the 21st century so that they may be compared with real events as they happen.
2019: computers pass limited forms of the Turing test; people begin to have relationships with computers; visual, auditory and tactile virtual reality enables people to realistically interact with physically distant partners; automatically driving systems installed in most roads (predicted by Ray Kurzweil1999)
2027: Crisis of 2020 over; First Turning (New High) begins (Strauss and Howe, 1997)
2029: Human - computer communication via direct neural connections[?]; humans don't work in production, agriculture and transport anymore; computers claim to be conscious and these claims are generally accepted (predicted by Ray Kurzweil1999)
2030: robots with monkey-like thinking capabilities, able to imitate tasks and solve simple problems, appear (predicted by Hans Moravec[?]1998)
2040: robots comparable in ability to humans appear; soon thereafter, they surpass humans in most abilities (predicted by Hans Movavec[?]1998)
2047: High over; Awakening begins (Strauss and Howe, 1997)
