@DrOct In accordance with the Gregorian calendar, the 21st (twenty-first) century, the current century of the Common Era, began on January 1, 2001, and will end on December 31, 2100. It is the first century of the 3rd millennium. In accordance with the Gregorian calendar, the current decade began on January 1, 2011, and will end December 31, 2020. The Gregorian calendar counts ordinally, there was no year zero, and we are still in the 202nd Gregorian calendar decade.