noun
A traditional Japanese celebration held on certain milestone birthdays (40th, 50th, 60th, etc.) to wish for long life. The term is somewhat formal and may be encountered in historical or cultural contexts.
祖父の還暦に算賀の宴を開いた。
We held a longevity celebration banquet for my grandfather's 60th birthday.
Composed of 算 (calculation, counting) and 賀 (congratulations, celebration), referring to the counting of years and celebrating the milestone. The exact historical derivation is uncertain, but the term is associated with traditional Japanese age-related festivities.