It is set on 1990, and based on Douglas Coupland's own generation, Jones. He was born in 1961, and the characters are the same age as he and his peers. He specifically states it is about those Gen Joneses who became the mainstream of X, and AT THE TIME he wrote it, they were considered X.
In 1982, those at the end of Gen Jones were considered part of Generation X. It has been noted several times that Gen Jones had gay more cultural markers and similarities in common with X than with the first half of the Boomers, some of whom are their parents.
*way more cultural markers
*1980-82
(I am weirdly fascinated with both Jones and X, and to a lesser degree with Boomers)