1) Anniversary 2) Day of remembrance 3) Tricentennial 1) Tricentennial 
• (a.) Including, or relating to, the interval of three hundred years; tercentenary. • (n.) A period of three centuries, or three hundred years, also, the three-hundredth anniversary of any event; a tercentenary.
[adj] - of or relating to or completing a period of 300 years
tricentennial adjective of or relating to or completing a period of 300 years