What's the difference between tricentenary and tricentennial?

Tricentenary

Definition:

(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.

Example Sentences:

(1) His work was published in 1691, and on the occasion of the Tricentenary of its publication, the "First International Symposium on Phlebotomine Sandflies" was organized.
(2) It is particularly appropriate for an assemblage of protozoologists to pay homage to this intrepid "philosopher in little things," a man with an insatiable curiosity about his wee animalcules, on the tricentenary of his discovery of them, since it was an event of such long-lasting significance.