How Happy Death Day 2U's Time Loop Works

Happy Death Day 2U Tree wakes up with fried, poofy hair

Warning: spoilers for Happy Death Day and Happy Death Day 2U are in play. If you haven’t experienced that event in all of its permutations, you should definitely put yourself in the loop.

Previously on “Mike Breaks The Time Space Continuum,” I got myself caught in a time loop discussing the ins and outs of Edge of Tomorrow’s continuous cycle of action, adventure, and romance. Just when I thought that’d be the reprieve I’d need to get out of my own loop, I was pleasantly surprised by the twist of getting caught in another, parallel time loop after the fact. Yeah, parallel universes and time loops apparently exist, and strangely enough that’s what we’re about to discuss in this week’s double feature.

While Happy Death Day 2U is going to be the main thrust of our discussion, there’s obviously some overlap with Happy Death Day that will come into play. Just when you thought it was safe to eat a red velvet cupcake, it’s time to loop back once again, as I’ve been giving this lecture to various degrees of success but haven’t finished it yet. Happy Death Day to us, dear readers.

Happy Death Day 2U Tree looks at the Sisyphus Quantum Cooling Reactor

The Time Loop In Happy Death Day 2U

Poor Theresa Gelbman (Jessica Rothe,) though you could call her “Tree” for short. Pity her not for her nickname, but rather for the fact that she’s been stuck in two different time loops on October 18th. The day of her own birthday, as well as that of her late mother Julie (Missy Yager,) Tree had to loop through a deadly chain of celebrations in Happy Death Day, and then got knocked back into the game yet again in Happy Death Day 2U.

What Causes The Time Loop In Happy Death Day 2U

By the end of Happy Death Day, we’re none the wiser as to how the time loop that caught Tree Gelbman in its snare began or ended. It just kind of happened for the length of a major feature film, and then ended when Tree became a better person, killing her would be assailant. Which left Happy Death Day 2U to explain that the reason Tree was looping through her own birthday, and then through a parallel universe version of that same day, was because of a faulty science project.

Developed with the help of Ryan Phan (Phi Vu), who just happens to be the roommate of Tree’s boyfriend Carter Davis (Israel Broussard), the Sisyphus Quantum Cooling Reactor, “Sissy” for short, was supposed to prove that on a molecular level, time could be stopped. Instead, all the machine did was cause four rolling blackouts, fried electrical circuits, broken bulbs all over campus, and $190.1 million in total worldwide box office across two films. Oh, and it locked a couple of Bayfield University’s students in a situation that “sucks the biggest mega balls in the history of shitty ball suckery.”

Who’s Caught In/Aware Of The Time Loop

Initially in Happy Death Day, Tree Gelman was the only person caught up in the time loop, with only Carter there to believe in her theory. But once Happy Death Day 2U came around, two other people found themselves in their own loops: brainiac science student/co-creator of Sissy Ryan Phan and Kappa Pi Lambda’s own queen bitch, Danielle Bouseman (Rachel Matthews.) As for the circle of friends who are enlisted to help decode the time loop’s mysteries, Ryan’s fellow researchers, Samar Islam (Suraj Sharma) and Dre Morgan (Sarah Yarkin) round out the list of figures in the know.

When Does The Loop Start/End

Happy Death Day’s original time loop was revealed to be triggered by a random firing of the Sisyphus Quantum Cooling Reactor on 12:01 AM, Monday, October 18th, 2017; an event we’ll name “Loop A.” “Loop A Prime” takes place under those same parameters, on the same date, just in a parallel dimension that makes up the majority of Happy Death Day 2U’s storyline. “Loop B” is the mini-loop we experience through Ryan Phan’s eyes, which takes place on Tuesday, October 19th, 2017; and also triggers a reset event as of 12:01 AM.

“Loop C” is the final loop, which we don’t know much about at this current moment. That’s the big sequel tease dangled at the end of Happy Death Day 2U, which sees Danielle Bouseman “voluntarily” dropped into a hell of her own. Of course, 12:01 AM is the best case scenario that ends the time loop, as the killer known as Babyface tends to end the lives of those involved in each version of the time loop we’ve seen so far.

Happy Death Day 2U Tree shows off her sweatshirt to Ryan

How The Time Loop Is Used In Happy Death Day 2U

Both Tree Gelbman and Ryan Phan are using the Happy Death Day 2U time loops to primarily do one thing: figure out how to close the loop, and restore the flow of time. It’s simple enough when Happy Death Day showed off the events of October 18th, as that film’s story was focused on Tree becoming a better person. But a thread that is seemingly resolved in the first film, only to return in the sequel, is Tree’s grief over the loss of her mother, Julie. Discovering that the Happy Death Day 2U dimensions’ version of October 18th sees her mother still very much alive, but sees Carter dating Danielle instead of her, Tree is left to make a choice of which dimension she wants to exist in.

What Are The Advantages Of The Time Loop

The greatest advantage to the time loop portrayed in the loops of Happy Death Day and Happy Death Day 2U is that the opportunity presents itself to turn Tree Gelbman from slightly evil sorority sister into a detective with an understanding of quantum physics. Working her way through suspects in Loop A, Tree is able to find out that roommate Lori Spengler (Ruby Modine) was her would-be assassin. Her jealousy over the affair between Tree and professor Gregory Butler (Charles Aitken) motivated her to release a serial killer to cover her tracks, while killing Tree in every variant of that day.

Happy Death Day 2U expands on Tree’s skills of deduction and memory to accomplish the new task of carrying each failed algorithm meant to close the time loop through to the next iteration. Which gives Tree a bonus objective, as she ultimately looks to have become a bit of a student in quantum physics. Though on top of delivering data to Ryan, Samar, and Dre’s scientific minds, Tree’s also got to figure out who’s behind the Babyface mask in Loop A Prime, which turns into a double whammy. Not only is Gregory Butler a Babyface killer in this loop, but so is his wife Stephanie (Laura Clifton,) as their mutual motive is to rid themselves of the complication to their lives known as… Lori Spengler.

What Are The Challenges Of The Time Loop

As with any time loop, the largest obstacle of Happy Death Day 2U’s loop, and by extension any other version, is that once the day resets, all progress is overwritten. With only Tree Gelbman or Ryah Phan remembering the events of past iterations in their respective loops, they have to reintroduce the same scenario to their friends over and over again. Plus, if someone Tree wants to survive ends up dying in any loop, much as Carter did in the second to last loop of Happy Death Day, she needs to reset the loop and hope he doesn’t die the next time.

Adding further complications to the party, Happy Death Day 2U introduces yet another wrinkle into the pudding: physical damage. It’s never fully explained, but through her sequel driving antics, Tree starts to take on some physical damage after a certain amount of deaths have occurred. An additional ticking clock thrown on top of figuring out the algorithm that closes the loop, there’s only so many attempts that can be made before her time runs out.

Happy Death Day 2U Tree and Carter kiss amid bursting light bulbs

How Does The Time Loop Finally Stop In Happy Death Day 2U

Thanks to Tree Gelbman sacrificing her life countless times, while acting as a living record of the research that went into the Sisyphus Quantum Cooling Reactor’s algorithm, Happy Death Day 2U finally sees Tree solving her temporal recursion errors by simply going home. Right as the mid-credits stinger starts up, Ryan Phan explains to Dre Morgan that the loop’s closing was thanks to an old fashioned physics fix:

It acted like a slingshot. When she jumped back into this dimension, the vacuum created by the centripetal force closed the loop.

So maybe Star Trek IV: The Voyage Home got it right, and a good slingshot maneuver can propel a person across the barriers of time. Though considering the power that Sissy was packing, and the intense mathematical equations that went into getting it up and running properly in the first place, you really do need the right slingshot. So unless you’ve got a quantum cooling reactor, or a Klingon Bird of Prey, you might not want to try this at home.

Happy Death Day 2U Tree flips the birds

Suck It Dean Bronson!

Wait… WE’RE FINISHED! We’ve just completed both Happy Death Day and Happy Death Day 2U’s time loop dissections, and we’ve arrived at the end! I politely request that both Dean Bronson of Bayfield University, every variant of Babyface, and the laws of time and space, kindly suck it, as I’m free. Not free from time travel, of course, as I’d never want that fate. I’m a traveler, and I must be allowed to roam the timestreams that are out there. Though I’m definitely not ruling out a return to time loops, as we’ve got some rather mythic ones lying ahead.

However, for our next journey through time and space, it’s time to go once again where no one has gone before. Reyes to Enterprise, one to beam up, as the next journey from here to there in the now and then is going to be all about Star Trek: First Contact. But, of course, don’t let that stop you from sending your suggestions as to which adventures you’d like us to wind back the clock with in the future! The CinemaBlend labs are always open, and I’m sure one version of me will be around to check the inbox. Now if you’ll excuse me, I need to see how many messages I’ve missed, thanks to the whole “delayed email in a time loop” scenario.

Mike Reyes
Senior Movies Contributor

Mike Reyes is the Senior Movie Contributor at CinemaBlend, though that title’s more of a guideline really. Passionate about entertainment since grade school, the movies have always held a special place in his life, which explains his current occupation. Mike graduated from Drew University with a Bachelor’s Degree in Political Science, but swore off of running for public office a long time ago. Mike's expertise ranges from James Bond to everything Alita, making for a brilliantly eclectic resume. He fights for the user.