Taylor Swift and Calvin Harris Split: A Look Back at Their Relationship and What Went Wrong

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It seemed like a match made in musical heaven.

When Taylor Swift and Scottish DJ and super-producer Calvin Harris began dating 15 months ago, they quickly became one of the most enviable celebrity couples ever to grace social media.

Though rumors of a romance first began when they were spotted getting close at Kenny Chesney's Nashville concert in March last year, social proof of their love started with Harris, 32, first posting pictures of Swift's beloved cats last April.

The duo then made their official outing as a couple at the Billboard Music Awards one month later.

They were also spotted that same month having a romantic dinner date at Giorgio Baldi in Santa Monica wearing matching all-black ensembles. Swift, 26, "seemed incredibly happy but also very at ease with Calvin," an onlooker said at the time.

Over the Fourth of July weekend, the duo cemented their love on Instagram when the "Shake It Off" singer shared an adorable shot of her boyfriend carrying her on his back, captioning it "Friendly relations between Scotland and America."

"There's a whole bunch of times when we've been hanging out and nobody's caught it," Harris told KISS FM UK that month. "You know, it's not like every single time we go out we get a photograph taken of us. That's not the case. But for me, though, it could be a lot worse and I'd still be like insanely happy with her so I'm good with it."

The good times seemingly continued for the couple throughout the rest of the year, with Harris growing close to Swift's tight-knit family.

Say It Isn t So! Taylor Swift and Calvin Harris Call It Quits After 15 Months

Over the holidays, the couple spent time with Swift's parents and her younger brother Austin in Vail, Colorado, where they dined out at Zach's Cabin and built snowmen in the winter wonderland.

Celebrating their one-year anniversary in March, Swift and Harris set social media ablaze with romantic snaps from paradise.

Both the entertainers shared sexy shots from their ultra-private getaway in the Caribbean, sparking vacation FOMO across the nation. "That time we finally took a vacation," the 1989 hitmaker wrote on one post.

"When she was on tour last year, he really missed her and it wasn't easy," a source told PEOPLE after their anniversary. "Of course they love each other, but they are not the type of people to rush down the altar."

Swift – who rarely opens up about her romantic relationships in interviews – also addressed her relationship with Harris for the first time in the spring.

At the iHeartRadio Music Awards in April, she publicly gave him a shout out during her acceptance speech, saying, "For the first time I had the most amazing person to come home to when the crowds were all gone and the spotlight went out, so I'd like to thank my boyfriend Adam for that," she said, referring to Harris by his real name, Adam Richard Wiles.

She also touched upon their "magical romance" in the April issue of Vogue. "I'm just taking things as they come," she told the magazine. "I'm in a magical relationship right now. And of course I want it to be ours, and low-key this is the one thing that's been mine about my personal life."

FLASHBACK: Taylor Swift and Calvin Harris Celebrate Their 1-Year Anniversary in the Cutest Way Possible

So what caused a seemingly picturesque romance to go south?

Indeed, both stars have had equally demanding work schedules keeping them apart. In January 2015, Harris struck a three-year residency gig to DJ at Las Vegas clubs at the MGM Grand and Caeser's Palace. He's also a highly sought after producer, whose current hit with Rihanna, "This is What You Came For" recently hit No. 9 on the Billboard charts.

Meanwhile, Swift was on tour for seven months last year and has been busy with work commitments this spring, including co-chairing the Met Ball last month. The star attended the event with her pals, and was again solo when she picked up an award at the 2016 BMI Pop Awards later in the month.

"There was no drama. Things just don't work out sometimes," an insider told PEOPLE. "No one cheated."