what is the novel's era?

Speak by Laurie Halse Anderson is set in a contemporary high school in what is likely the late 1990s. Though the author never says the precise era, it's safe to assume that the novel is set in the Cenozoic Era, which is the modern era.
The setting of the book is in Syracuse, New York in the 1990s. Since the novel was published in 1999 and there are no anachronisms in the text that would suggest a different time period, it's safe to assume that the events took place around the publication year. Much of the story takes place at Merryweather High School, where Melinda is a student. The novel is split into four marking periods, and the story takes place over the course of a year.
Eras are very long spans of time. The Cenozoic Era covers the time from 66 million years ago until the present time. The Cenozoic Era is partially defined as being the era of mammals and means the era of modern life. It is the setting for Speak.
https://www.ck12.org/c/biology/cenozoic-era/lesson/Cenozoic-Era-The-Age-of-Mammals-BIO/?referrer=concept_details