Yearly celebration of a date or an event

One word substitute is Anniversary.

Centenary: the hundredth anniversary of a significant event.
Jubilee: a special anniversary of an event, especially one celebrating twenty-five or fifty years of a reign or activity.
Anniversary: the date on which an event took place or an institution was founded in a previous year.
Birthday: the anniversary of the day on which a person was born, typically treated as an occasion for celebration and the giving of gifts.