Sugiro utilizar as opções "many happy returns'' or ''many happy returns of the day'' no contexto mencionado.
= a conventional greeting to someone on his or her birthday. [Collins]
= A greeting, usually for birthdays, in reference to the passing year; Happy birthday!
The earliest attributable use was by Lady Newdigate in a letter written in 1789 (and published in Newdigate-Newdegate Cheverels in 1898): Many happy returns of ye day to us my Dr Love. [Wikitionary]
Bons estudos. Compartilhe a dica.