Sentence:  But he did not notice , and was already backing the car down to the road , saying `` Toot-toot '' ! to the stump of a tree as he passed it , the same stump which had impaled the car of many a guest in the past thirty <WSD>years</WSD> and which he refused to have removed . 
Meaning of the word marked with <WSD> tags:  a period of time containing 365 (or 366) days