2000 (MM) was a leap year that started on a Saturday of the common era, in accordance to the Gregorian calendar with any other year. It was the 2000th year of the Common Era or the Anno Domini designation. 2000 was also the last year of the second millennium and of the 20th century. It was also the first century leap year since 1600. The year 2000 was the first year of the 2000s decade. Popular culture holds the year 2000 as the first year of the 21st century and of the 3rd millennium, due to a tendency to group the years according to decimal values, as if year zero were counted. According to the Gregorian Calendar this distinction falls to the year 2001, also because the first century back then was retroactively said to start with year AD 1. Since the calendar has no year zero, its first millennium spans from years 1 to 1000, inclusively, and its second millennium from years 1001 to 2000. See more at Millennium. The year 2000 was the subject of Y2K concerns, fear that computers could not shift from 1999 to 2000 correctly. However, by the end of 1999, some companies have upgraded to new, or existed their shifting software. Some even obtained Y2K certification. In the actual event, relatively few problems occurred.