Sentence:  At four o ' clock , or four thirty , the coming of the newsboy marked the end of the <WSD>day</WSD> ; he tossed a paper toward every front door , and housewives came down to their steps to pick them up and read what their neighbors had been doing . 
Meaning of the word marked with <WSD> tags:  the recurring hours when you are not sleeping (especially those when you are working)