century.
1. The end of a millennium makes everyone aware of the difficulty of reckoning when a century (let alone a millennium) truly begins and ends. In arithmetical terms, the 21st century should be reckoned as beginning on 1January2001, since 2000 is strictly the last year of the 20th century (and 2nd millennium). But who is going to wait until the end of the year 2000 before celebrating the millennium? In popular usage, a new century begins ...