The 27-year-old actor took to Twitter on Monday two days after their anniversary to share his love for Sami Miro.
Zac wrote: "Happy anniversary baby :) I love you. September 5th @SamiMiro" and although his message was late, Sami responded with "Time flies when you're having fun. Happy anniversary baby. I love you too September 5th @ZacEfron (sic)."
Zac shared a picture of him tenderly kissing his girlfriend behind a sheer curtain while Sami posted a close-up picture of them both smiling.
Stylist and model Sami recently admitted that dating the Hollywood hunk has changed how she uses social media, particularly Instagram.
She told ELLE.com: "I've never spoken about us before, but, um, it's definitely different. I think that you have to take that [kind of attention] with a grain of salt... It kind of just comes with the territory, and I know there's no really changing that, so you have to just embrace it...
"I'm not trying to hide anything in my life. If I was dating someone who wasn't in the limelight, I might have more photos on [Instagram] of our relationship, but I do think it's important. I mean, it's what is going on in my life, and I think that my social media can still represent that."
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