In time for the holidays, Cortana has gotten a little more festive, adding a new setting for "special days". The virtual assistant can now help you celebrate holidays and other important dates with special greetings, games, and more.
In Cortana's Notebook, you can now scroll down to find the new Special Days section. Head there to turn on the assistant's ability to mark special occasions, then tap the save button, and you're all set. This feature should be available to all Windows Phone users now.
Thanks to David for the tip