Definition - What does Cake Day mean?
The term “cake day” refers to an anniversary celebration – the term is most commonly used to describe the day of the year that a Reddit user opened his or her account. Although many attribute the origin of this term to the Reddit community, other platforms have begun to use it, such as Imgur. Some people may also use the term to refer to their actual birthday.
Techopedia explains Cake Day
The Reddit platform, described as a modern-day online bulletin board, has all kinds of rituals and conventions attached to celebrating a user’s cake day. Users may post pictures of family members or pets, or get a number of upvotes to their posts, or interact in certain ways with other Reddit users. In general, Reddit created its own take on the connection between someone's birthday and the physical birthday cake used to celebrate. Many users are amused when they figure out that “cake day” is not their birthday, but the day that their Reddit account was “born.” For the most part, all of the cake involved in a Reddit cake day is digital.