Was browsing the site because of this deal and saw it, however the birthday component was already in the Wiki, yet no one shared it :)
When will I receive my complimentary slice of cake?
You will receive an email at the beginning of your Birthday month to notify you of your complimentary slice of Birthday cake. This will automatically be uploaded to your card and will expire at the end of the month.I haven’t registered my card, can I still use it?
Un-registered cards can still be used in store to accrue points and gain small complimentary coffees but by registering online you will receive a complimentary small size hot beverage for registering as well as a slice of birthday cake anytime in the month of your birthday.
Caaaake! :P