No, not the clock that changes color when you blow on it. Rather this was how DC tried to keep fixing the continuity problems left ("Ha ha 'left.'" - Hawkman) after Salt and Pepper Lantern gave 60 years of DC continuity a hug. In an effort to get around that, Hypertime was introduced. Basically, it was a many worlds theory that used time travel to work around the "only one Earth" rule - everything happened, but divergences created an alternate timeline instead of an alternate Earth, and some things happened concurrently and were merged together by big events.
Hypertime was Schrodinger's Continuity. Schrodinger's Cat, a thought experiment from quantum mechanics, says imagine a cat in a box that is attached to a button that has a 50/50 chance of flooding the box with poison gas if pushed. After you push it, you don't know whether the cat is alive or dead until you open the box and look. Quantum theory says that the cat exists in both states - alive and dead - until the box is opened. Hypertime says that at the moment you push the button, two distinct timelines emerge: one (call it the You-Dodged-Abuse-Charges timeline) where the cat is alive, and one (Earth You're-A-Pet-Murdering-Monster) where the cat is dead. The latter also happens to be the Earth that Man of Steel was set on.
The language runs together because they're more or less the same thing with different names. Outside of comics, this is one of the most commonly used tropes - it's been in everything from Star Trek to the Zelda games to story mode from Mortal Kombat 9. Even in the DCU, it's still sort of used - the Beyond comics are considered the canonical future of the DCU, but there's all sorts of mucking with time going on in "Future's End" right now. As a tool, though, it was not broadly successful, and has been passionately disavowed by current DC bosses more than once.
The laziest and usually most hilarious tool for solving continuity problems is the retcon. You see half-assery like this everywhere from Sherlock Holmes' "I wasn't dead! I tricked you!" to Professor X's telepathic macks on Jean Grey to Kyle Rayner's CIA agent dad to what should be a mandatory postscript for every Nick Fury story, "LOLJKLMD."
Retcons are new stories that retroactively change something about a character's history. Sometimes they work: somehow, against all odds, Hal Jordan's return from the dead not only makes sense, but is a perfectly reasonable and satisfying comic story. The same goes for Bucky/the Winter Soldier: that was one of the best Captain America stories ever. But for every story where you find out about the twin Professor X strangled in the womb that's now back and controlling the Shi'ar Empire and trying to kill him, you get "oh hey turns out Darth Vader built C-3PO." FYI, the X-Men one was the good one in that comparison.
Every revelation that Animal Man is the animal equivalent of Swamp Thing in the hierarchy of life on Earth...sees two like Xorn's brother Xorn pretending to be Magneto posing as Xorn, or finding out that Gwen Stacy had a weak spot for old guys with finger waves, or turning the JLA Watchtower into an episode of SVU, or Superboy punching the walls of reality so hard that Jason Todd came back to life. The bad reeeeeeeeeeeeeeeeeeeeeeeeeeeeeally outweighs the good here, in the same sense that Jupiter outweighs Mercury.
2. Marvel Time
Marvel Time is technically a "retcon," but it's not precisely that. Marvel Time says that Fantastic Four #1 was published between 10 and 15 years ago today, no matter what day "today" is. It's a hard rule with ambiguous enforcement. It leaves enough wiggle room to allow some continuity quibbles to sneak by, if you also operate with a sort of "try not to think too hard about it, it's fine" mantra.
The only real problems it faces are characters who are tied existentially to specific events - Captain America and Magneto and their respective related characters are tied definitionally to World War 2. The Punisher served in Vietnam. Warpath loves mediocre grunge. So unless Dazzler was magically part of the big underground disco scene in the early aughts, making her a contemporary of mid-stage Daft Punk and Jamiroquai and you know what? Nevermind, Marvel Time is perfect.
1. To Hell With It, EVERYTHING COUNTS!
IDW is the 34th company to hold the license to publish Transformers and GI Joe comics. Their approach to continuity seems to be "it all happened, and here are books that follow up on your favorite stories!" For obsessive compulsives trying to hammer everything into a unified timeline, this is muy bad. For people who love the old Marvel G1 comics and want more from the same people, this is great. For people who like Axe-Copish crossovers of the two, this is excellent.
This is also the approach that Rob Liefeld is taking in farming out his Extreme books. There's no doubt that the person who takes over Youngblood next isn't going to spend years writing the creation of the Earth Empire to line up with Brandon Graham's (AMAAAAAAAAAAAAAAAAAAAAAZING) Prophet story. He's letting his writers write, letting them tell the stories they want to tell first and worrying where it all lines up later. Marvel and DC have occasionally made nods towards this, but there's always been some editorial necessity that precludes them from going all the way with it, and while the shared universe has certainly led to some amazing stories, the best comics, company or creator-owned, are the ones that only have to care about their internal continuity.