Sentence:  Of course, a show might start at a certain time, and one must place bets at the sports book at the right time, but for the most part, day <WSD>runs into</WSD> night and night <WSD>runs into</WSD> day without notice or comment. 
Meaning of the word marked with <WSD> tags:  To blend into; to be followed by or adjacent to without there being a clear boundary.