Norah O’Donnell, Lester Holt and David Muir often journey to global hot spots and scenes of national interest. In recent weeks they’ve been engaged in travel of a different sort – through time.

ABC, NBC and CBS have all begun re-airing their various evening-news programs in the early morning via a select group of stations owned by their parent companies or through affiliates. Under Nielsen rules, the networks can use the viewership of these repeats in tabulating ratings (whether advertisers are thrilled about the matter no doubt hinges on who, exactly, is watching in the dead of night), but the re-purposed newscasts also give rise to the notion that the TV companies can no longer keep evening news solely in the slot between “Jeopardy” and “Inside Edition.”

After running snippets of “CBS Evening News” in its overnight news package for some time, CBS News last week began airing distinct repeats of the daily broadcast, including one that airs at around 3 a.m. on New York’s WCBS. Near the start of the current TV season, ABC News began putting up early-morning re-airs of its “World News Tonight” in nine different markets. NBC in July began re-airing “Nightly News” in post-midnight hours in 11 markets.

Each time one of the trio starts a late-night salvo, it encourages the others to do so as well, in an effort to “level the playing field,” according to one person familiar with the deep-night tactics.

“What you are seeing is the continued struggle for those broadcasts to stay relevant,” says Mark Lukasiewicz, dean of the Lawrence Herbert School of Communication at Hofstra University and a former senior vice president at NBC News. “Outreaches into overnights are getting that extra tenth of a ratings point, which right now can be the difference in bragging rights between the number one and the number two. Any way you can eke out a little more audience? That can be valuable.”

ABC News, NBC News and CBS News declined to make executives available for comment.

The networks place new emphasis on finding non-traditional slots for the programs after years of critics scoffing that younger viewers find their news elsewhere – and certainly aren’t home at 6:30 p.m., when the shows typically run.

These days, a news aficionado might call up a podcast of “CBS Evening News,” complete with commercial backing from Liberty Mutual; watch a stream of ABC’s “World News Tonight” on Hulu; or even check out separate in-depth pieces under the “NBC Nightly News” rubric on a special website. CBS re-runs O’Donnell’s newscast on its streaming-video outlet, CBSN, at 10 p.m., and NBC re-airs “Nightly” on its live-streaming service NBC News Now at 10 p.m. and 10:30 p.m.

As primetime ratings shrink in tandem with a consumer migration to streaming video and on-demand viewing,  the evening newscasts are also starting to take on a different allure. In some cases, they capture some of TV’s biggest crowds. “World News Tonight,” for instance, often wins more viewers overall than many of the programs in ABC’s primetime lineup. To be sure, the primetime programs likely attract more of the younger viewers advertisers desire – and for which they pay a premium. With some of that in mind, spreading the evening news to new places can still help boost the format to new audiences.

“In an on-demand world where the customer is in charge, even legacy news programs have to offer convenience, not just coverage,” says Andrew Heyward, the former CBS News president and media consultant who is doing research at MIT Media Lab and Cronkite School of Journalism.

The overnight plays are of greater importance to evening-news economics.  The three networks are locked in an eternal Coke-versus-Pepsi-versus-Dr Pepper battle for ratings dominance, and every extra view can help. Consider that just 3,000 viewers separate “World News Tonight” and “NBC Nightly News” among viewers between 25 and 54, the demographic most coveted by Madison Avenue, season to date as of November 1 according to Nielsen. Meanwhile, CBS News is trying to gain traction for the O’Donnell-led “CBS Evening News” after a series of anchor changes in recent years has spurred a ratings downturn at that program.

There’s reason to cast about for extra attention. After notching a recent high of $552.4 million in advertising in 2017, the three broadcast-network evening newscasts have seen Madison Avenue look elsewhere in recent years, according to Pew Research Center. Combined ad spending on NBC’s “Nightly,” ABC’s “World News” and CBS’ “Evening” fell 6% last year, to about a little more than $518 million, according to Pew data. It’s the first time in six years that ad spending on the three programs has declined.

Throwing reruns of the earlier news broadcast to the lobster shift can have its advantages. “NBC Nightly News” finished the 2018-2019 season with a 26,000-viewer win in the 25-to-54 demographic, according to Nielsen, and rivals believe the re-airs helped NBC’s position.

Some of the evening-news extensions surface even before the sun goes down. ABC News began airing a simulcast of the east coast airing of “World News Tonight” in San Francisco at 3:30 p.m. in January of 2017, and in Los Angeles at the same time a year later. According to Nielsen, those two programs have lent “World News Tonight” a boost of 50,000 viewers between 25 and 54 – almost half of 105,000 viewers in that category often captured by the range of “World News” repeats. Without those viewers, the newscast might not be as competitive in that category, and NBC’s newscast would dominate.

“We are thrilled LA asked to air our newscast live at 3:30 in the afternoon,” ABC said in a statement when the Los Angeles rerun debuted in 2018. “This is about the hunger for news in this moment and the strength of our newscast.”

NBC was first to discover the power of wee-hours maneuvering. In 2015, the network tested airing repeats of “Nightly” between 2 a.m. and 4 a.m. on stations in Knoxville, Atlanta, Seattle, Minneapolis, Denver, Cleveland, St. Louis, Portland, Charlotte and Buffalo, all just as anchor Holt was taking the newscast over from Brian Williams. NBC stopped airing national commercials in the broadcasts  – disqualifying the network from counting it as part of Nielsen ratings – after press reports about the effort prompted select media buyers to complain.

Not too long ago, the re-airs were fun. NBC for some time aired a second run of the fourth hour of “Today,” when it was hosted by Kathie Lee Gifford and Hoda Kotb. That  2 a.m. rebroadcast, which started in 2011, filled replaced a late-night poker hour, but also put the program in front of college students, insomniacs and night-shift workers. At the time, the move was viewed as something done largely for kicks. The current late shift for the evening-news programs is anything but.