From the White Wolf Wiki, the most complete White Wolf reference

The Nova Age is an in-character term for the period when novas were largely active on Earth. During the Unity Age, denizens often refer to the Nova Age as the Aberrant Age. This timeframe is largely the focus for the Aberrant game line, thus it is also known out-of-character as the Aberrant Era, or thematically as the Age of Sacrifice.

The Nova Age begins with the explosion of the Galatea space station in 1998.

As the years progress, novas become progressively more and more violent and insane, leading to the Aberrant War in 2049.

It's uncertain if the Aberrant War counts as part of the Nova Age, but the Nova Age certainly does not encompass anything later than 2061, when the War ends.

See also: Inspiration Age, Unity Age