Illustrative example. The dates and amounts below are provided for practice.
You know a friend's birthday is December 31 and want to see the remaining days without recording their age. A yearless countdown can answer that question directly.
Enter Birthday Month 12 and Birthday Day 31. Leave Birth Year blank and set Calculate As Of to December 29, 2027. Calculate. Next Birthday is December 31, 2027, Friday, and the countdown is two days.
The output has no Current Age row because the year was not supplied. A placeholder year would create an age claim, so keep the optional field empty.
Read the number as an interval
Two elapsed days separate December 29 and December 31. Calling December 29 Day 1 would make the birthday Day 3, but this is a countdown rather than inclusive day numbering.
If you later learn the birth year, enter it and calculate again with the same reference date. The next month-and-day occurrence remains unchanged, while an age row becomes available. For a recurring record, use Every year. A one-time dated party on New Year's Eve belongs in its own record, especially when its venue or schedule may change.