Illustrative example. The dates and amounts below are provided for practice.
A June 8 birthday has already passed when you review the list on June 9, 2027. A negative “next birthday” countdown would confuse the next occurrence with the one you missed.
Use month 6, day 8, no birth year, and Calculate As Of June 9, 2027. The result points to June 8, 2028 and shows 365 days remaining.
Why this gap is 365
The reference date begins one day after the 2027 occurrence, but the interval also crosses February 29, 2028. Those effects balance in this particular example. Do not infer that every just-passed birthday is always 365 days away.
The previous birthday is one elapsed day before the reference date. The next birthday is 365 elapsed days after it. An inclusive series beginning June 9 would call the next target Day 366.
A belated message concerns the previous occurrence, so use that date in your note. Save an annual tracker record for future preparation. Do not change the birthday to June 9 merely to remove the feeling that it was missed. That would move the recurring event permanently.