Knowing a friend's birthday does not require knowing their age. A month and day are enough to find the next occurrence, its weekday, and the number of days remaining.
Enter the known month and day and leave Birth Year blank. The form accepts February 29 without a year. Choose the person's common-year observance so the tool can select February 28 or March 1 when needed.
The same date, two different questions
For a birthday on June 8, a reference date of June 1 gives seven days remaining regardless of whether the person was born in 1990 or 2005. Their age differs, but the annual countdown does not. If you later learn the year, enter it to show completed age as well.
A yearless record in the tracker stays yearless after saving. Use annual repeat. Do not enter the current year to make a form look complete. That creates a real birth date and can show an incorrect age.
When a full date matters
A school form or eligibility decision may need a full date and rules specific to that purpose. Ask for the missing information rather than using the countdown to infer it. If someone gives you an age without a birth year, the date when that age applied may also be unknown.
For a private birthday list, the month and day often provide all the information needed to buy a card or arrange a call.