Fans were quick to comment on his gracious post, writing things like, "Keep making the world a better place," "So proud of you," and "better late than never!!!"
The band's actual anniversary was on Saturday, with Harry Styles, Niall Horan and Louis Tomlinson all sending out tweets to their fans thanking them for their love and support over the years.
"Six years. I have no idea how to say thank you for all your support," Styles, who reportedly signed his own solo contract with Columbia Records last month, shared. "For everything you are, and everything you've done, thank you."
Horan echoed Tomlinson's sweet sentiments, writing, "6 years. Wow! As Louis touched in his message, each one of you have played a part in changing lives. You are the best fans in the world as you know…Thank you so much for everything so far."
6 years . wow ! As Louis touched in his message , each one of you have played in a part in changing lives..