What is happy cakeday?

"Cakeday" is a term used on social media websites such as Reddit to refer to the anniversary of a user's creation of their account. It is considered a happy occasion and users often receive messages of congratulations and well wishes on their cakeday. Some users also celebrate by posting pictures of cake or other desserts. The tradition of cakedays is thought to have originated on Reddit in 2008 and has since spread to other social media platforms.