The first 10 years are 1 through 10. That is the first decade. Consequently, the next decade is years 11 through 20.

The first century is years 1 through 100. Therefore, the second century is years 201 through 300.

The first millenium is years 1 through 1000. Therefore, the second millenium is years 2001 through 3000.

There is no year zero.