birthnight

plural birthnights

1. The night of someone's birth.
2. The night of someone's birthday.

   And of the Angelic Song in Bethlehem field, / On thy birth-night, that ſung thee Saviour born.

   1671, John Milton, “The Fourth Book”, in Paradise Regain’d. A Poem. In IV Books. To which is Added, Samson Agonistes, London: […] J[ohn] M[acock] for John Starkey […], →OCLC, pages 104–105, lines 502–503

   1 more example

   he was on his way home and was going to take her out to IHOP for a late night birthday. I guess the best thing to have done, had I known , would have been to wish her a Happy Birthnight.

   2018, Norman Ross, Pater Noster in Condoland