Today is a momentous occasion for 5 Seconds of Summer's Calum Hood: the artist is celebrating his 20th birthday! Gone are Calum's teen years, and along with it, some seriously memorable throwback styles.
Each of the guys of 5SOS has transformed their fashion senses and hairstyles since starting the band, and that's exactly what we're celebrating today.
Click through the gallery to see photo-proof of the band's complete style evolution. Then, make sure to wish Calum a happy birthday by commenting below!