The rule stating that if you are dating someone or "talking" to that person, you cannot make them choose any plans for future engagements within 10 days of their actual birthday. UNLESS that person requests to make the plans. All other plans must be made by the person whose birthday is not within 10 days.
Dylan: Caroline, you have to make the plans for what we do tomorrow.
Caroline: No I don't you ginger, my birthday is in 8 days and its the birthday rule that everyone knows.