tredecennial means A period of thirteen years. Lexicurio rates it Rare gem — a strength score of 82 out of 100.
Etymology
Latin trēdecennium + English -al or Latin trēdecim + English -ennial
noun
- A period of thirteen years.“The tredecennial covered by the period of the survey was in a sense a most remarkable one; for it includes, with almost exact divisions, three significant sub periods: the prewar, the war and the post-war.”