Press the menu button on your cable remote and you’ll see the schedule lineup in a neat grid. Almost all TV shows start on the hour or half-hour, and this has been the case since the early days of television—with one notable exception: late-night talk shows on the big broadcast networks. Jimmy Fallon, Stephen Colbert, and Jimmy Kimmel all begin at 11:35 p.m. eastern time, and the shows that follow them also begin a few minutes after the half-hour. These are virtually the only shows on American television that begin at a time not ending with a zero. How did late-night shows get these irregular time slots?

You can partially blame Saddam Hussein.

At the start of the 1990s, affiliates “had been clamoring … to grab more time away from the networks,” Bill Carter—a former TV writer for The New York Times and author of The Late Shift: Letterman, Leno, and the Network Battle for the Night and The War for Late Night: When Leno Went Early and Television Went Crazy—tells mental_floss via email.

Local TV stations, which contract for programming from national networks like ABC, CBS, and NBC, wanted more airtime for their newscasts. Carter says there was special pressure on NBC, because they demanded more time from their local stations during late-night hours for national broadcasts. To be an NBC affiliate at that time meant dedicating two hours every weeknight to The Tonight Show Starring Johnny Carson and Late Night with David Letterman. While CBS, ABC, and Fox had some programming after 11 p.m., there was no block of late-night TV as permanent and unshakable as NBC’s.

“Some NBC stations were pushing the idea of moving The Tonight Show [to midnight],” Carter says, “which might have killed the franchise.”

When the first Gulf War began in the summer of 1990, the affiliates intensified their campaign for more news time, insisting they had to cover the conflict. NBC acquiesced by temporarily moving the start of its late-night block from 11:30 p.m. to 11:35 p.m. But once the local stations had those five precious minutes, they didn’t want to give them back.

Johnny Carson, who had hosted The Tonight Show for nearly 28 years at that point, was infuriated over the bump. "He understands the TV business and knows you never get that time back," Carter says of Carson's thinking at the time. "He fears the next move will be an 11:45 p.m. start and then midnight." But since Carson had been planning to retire in a couple of years, "he let it happen without real protest."

Once NBC gave its affiliates an extra five minutes for newscasts, the other networks followed suit. CBS didn’t want to seem like it was offering its affiliates a rawer deal, so when David Letterman began his Late Show on the network in 1993, CBS slotted the program at 11:35 p.m. ABC also slid its news show Nightline to 11:35 p.m. and moved Jimmy Kimmel Live! to that time slot in 2013.

A standard was set for the big networks, and it helped broaden the late-night landscape. "This open[ed] an opportunity for cable, which starts its late night at 11 p.m. and 11:30 p.m.," Carter says, "creating the Jon Stewart/Stephen Colbert phenomenon, as well as [Cartoon Network's] Adult Swim." Starting in the early 2000s, those cable lineups managed to chip away at the big networks' once-unassailable ratings leads.

So, ultimately, Johnny Carson had the last laugh.