UPDATED: There will be no seamless transition on CBS’ Late Show. The Late Show With Stephen Colbert will premiere on September 8, CBS chairman Nina Tassler announced this morning. That is more than three months after David Letterman wraps his 21-year run on May 20.

“I have nine months to make a show, just like a baby. So first, I should find out how you make a baby,” said Colbert, who ended his Comedy Central late-night show The Colbert Report last month.

Over the summer, CBS will air encores of primetime series at 11:30 PM. Asked later about the plan, which will pit drama and comedy reruns against originals of Jimmy Fallon and Jimmy Kimmel on NBC and ABC, possibly hurting new 12:30 PM CBS host James Corden. “Look, we have an opportunity with our hits to introduce them to a new audience over the summer,” she said. “We have three (original) scripted series (in primetime) on during the summer, which gets people in the mood to watch scripted content at 11:30 PM at night.”

CBS also is in talks with Letterman about special programming leading to his sendoff, Tassler said.

She noted that Colbert is bringing “almost everyone from Colbert Report with him” to Late Show. She shied away from any details on the format of Late Show With Stephen Colbert but pointed to comments made by Colbert that he plans to have guests. “It will be parts traditional, though some things he would want to do differently,” she said. “He is putting a lot of attention on the show, which he still wants to be topical, relevant and dealing with current events.”