Two thousand, A.D.

2000 (MM) was a century leap year starting on Saturday of the Gregorian calendar, the 2000th year of the Common Era (CE) and Anno Domini (AD) designations, the 1000th and last year of the 2nd millennium, the 100th and last year of the 20th century, and the 1st year of the 2000s decade. 2000 was designated as the International Year for the Culture of Peace and the World Mathematical Year. Popular culture holds the year 2000 as the first year of the 21st century and the 3rd millennium, because of a tendency to group the years according to decimal values, as if non-existent year zero was counted. According to the Gregorian calendar, these distinctions fall to the year 2001, because the 1st century was retroactively said to start with the year AD 1. Since the Gregorian calendar does not have year zero, its first millennium spanned from years 1 to 1000 inclusively and its second millennium from years 1001 to 2000. (For further information, see century and millennium.) The year 2000 is sometimes abbreviated as "Y2K" (the "Y" stands for "year", and the "K" stands for "kilo" which means "thousand"). The year 2000 was the subject of Y2K concerns, which were fears that computers would not shift from 1999 to 2000 correctly. However, by the end of 1999, many companies had already converted to new, or upgraded existing, software. Some even obtained "Y2K certification". As a result of massive effort, relatively few problems occurred. The eighth year of the post–Cold War era, significant conflicts included the Second Chechen War in the Caucasus and the Second Intifada in Israel and Palestine. This was the first year of continuous physical human presence in space, as Expedition 1 began on the International Space Station.