Taylor Swift and Calvin Harris celebrate first anniversary together!

Can you believe Taylor Swift and Calvin Harris have been dating for a WHOLE year already?

That's a huge achievement in Hollywood standards! And to celebrate their love for one another and their special milestone, Calvin posted a video on Snapchat of his lady love holding a handmade cake covered in chocolate icing with red love hearts that '1 Year' written across it.

Aww!

Taylor Swift and Calvin Harris. Photo: Getty

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In a video posted to Calvin's Snapchat account, Taylor can be seen nodding as she showed off her anniversary pressie.

Taylor also revealed her beau had got her a gold heart-shaped locket engraved with the date 3-6-2015 on it.

"One year down," she captioned on the snap posted to Instagram.

"He bought the locket all on his own. Calvin is not a flashy guy when it comes to gifts and he knows Taylor appreciates the small meaningful things, so he thought this would be the perfect gift," a source tells E! News.

"Taylor is a true hopeless romantic kind of lady and she thought Calvin really outdid himself with this gift. He had surprises for Taylor all throughout the day."

"Calvin knows that Taylor is the woman for him," adds the insider. "Out of all of Calvin's relationships, he seems the happiest with Taylor. He always says to all of his friends that Taylor is marriage material."