mr.green has little time today,

你说得对。是does。has有两个意思,一是实义动词,义为“有”；一是助动词,用于现在完成时里面,无意义。任何实义动词都不能直接带not,而要借助动词do/does/did来带not。如：He has a nice book。---He doesn't have a nice book。只有助动词、系动词be、情态动词才可以直接带not。如：He has closed the door already。----He hasn't closed the door yet。