the cake appears on the date that you set as your birthday when you were signing up. it is one of those bitcointalk features that few people notice.
if you set the real date then happy birthday otherwise happy fake birthday
I never notice this feature and you are right only few people notice this feature. Maybe it's because I did not set any date on my profile that's why I never knew that it really exist. To OP: Anyway, happy birthday/happy fake birthday. Happy new year to all. Wish you good luck and many more crypto knowledge to come and be safe from scam and phishing sites.