Eighteen years, 19 seasons, 419 episodes: That’s how long “NCIS: Naval Criminal Investigative Service” (“NCIS” to you and me) has been on our TV screens (viaIMDb).

In the nearly two decades since the series' first episode aired in 2003, its online grid, CBS, has kept “NCIS” in its regular slot of Tuesday at 8 p.m. Until now, that is.

Not only is Season 19 of CBS’s leadoff hitter changing its 18-year-old time slot, but “NCIS” is moving days, too (viaDigital Spy).

Mark Harmon Plays Leroy Jethrow Gibbs in NCIS

Starting September 20, 2021,Season 19 of TV’s most-watched dramais moving to Mondays at 9/8c, airing opposite “The Voice,” “Dancing With the Stars,” and “Monday Night Football” on their respective channels, which could spell a dip in viewer numbers compared to its regular Tuesday night slot (viaTVLine).

According to TV Line, “All Rise,” which aired at 9 p.m. on Mondays through the 2020-21 season, averaged 5.7 million total viewers, whereas “NCIS” averaged 12.6 million viewers during the same season in its original Tuesday time slot.

NCIS' time slot change will lead into its spin-off series

However, CBS hopes that the change in schedule for “NCIS” will bridge the drama gap between a block of sitcoms (“The Neighborhood” and “Bob Hearts Abishola”) whilst also making room for the highly anticipatedspin-off series, “NCIS: Hawai’i,“which follows its parent series on Mondays at 10 p.m.

“We hope to improve the [Monday] time period significantly, and we hope that it can be a strong lead-in to help launch ‘NCIS: Hawai’i,'“CBS Entertainment president Kelly Kahltold TV Line at the Television Critics Association summer press tour (viaExpress).

The cast of NCIS celebrating 200 episodes with cake.

“We realize that we can’t take [the time slot change] for granted, we have to help educate people and let them know where it’s moving to.”

“I will say that fans of that show are a diehard bunch,” Kahl added, “so I don’t foresee losing a lot of them with the time period change.”

Hopefully, this means that the popularity of the long-running show isn’t starting to wane, and the change in the schedule to move “NCIS” to Monday nights is just that a change in schedule to help lead in freshman spinoff “NCIS: Hawai’i.”