yearday

noun5

1. •
   A particular day numbered from the first day in the year, without regard to month divisions.

   • ... T₁max the maximum (cloud-free) daily total transmittance at a location with a given elevation and near-surface water-vapor pressure on a given yearday, […] — 2000
2. •
   (nonstandard, rare) An annual day; the anniversary of an event or occasion.

   • To wit, on certain year-days he would tarry alone in his tower, and his lamp might be seen gleaming till midnight. — 2020
3. •
   (rare) Synonym of anniversary, a day occurring in a yearly cycle.

   • The Second Advent of Christ to remove to heaven his waiting people takes place at the end of the yearday sixth vial in accordance with his personal announcement, […] — 1887
4. •
   (nonstandard, rare) Synonym of birthday, the anniversary of one's birth.
5. •
   (rare) Synonym of deathday or (Christianity) year's mind, the anniversary of a person's death, particularly as observed with a requiem mass or other commemoration.

   • The younger children remained at Bytham for a year, and saw their brothers again only at Leicester, on the yearday of Mother's death. — 2009