Tomorrow begins a new decade. This means that the new century and millennium began on January 1, 2001.
Folklore has it that it began on January 1, 2000. Folklore is very stubborn.
Since there was no year “0” the first year of the first A.D. millennium (only known looking back, of course – but as far as dates are concerned) was A.D. 1. The first decade of the first millennium was thus A.D. 1 – A.D. 10 inclusive.
From that you can figure out the rest.
The wikepidea comment that “The 2000s was the previous decade that started on January 1, 2000 and ended on December 31, 2009” is wrong. If that were the case, then the very first decade of the first A.D. millennium would have had only nine years.
Thus, tomorrow, a new decade begins. In the grand scheme of things this probably doesn’t matter much. But I thought something trivial might be good on the last day of the first decade of the first century of the third A.D. millennium.
Happy New Year!