Webster's Revised Unabridged Dictionary · 1913

nineties

nineties , noun, plural

1.
The decade from 1890 to 1899; as, the gay nineties.
2.
The decade from 1990 to 1999; as, they spent a ton of money to solve the Y2K bug in the nineties.
3.
The time of life between ages 90 and 100.