什麼時間 is used to indicate "what time" as a question. For example, if I said "現在世界各地是什麼時間？" it would mean "Right now all over the world what time is it?" 什麼時候 means "When?" For example, "你通常什麼時候吃蛋糕？" means "When do you usually eat cake?" In short, the first is used to indicate "when" in a literal time sense, but the second is used to indicate "when" the time of an event happened, either as a question or as a statement.

no, must use "shén-me shí-hòu" for "when?" stating the time of happening smth while "shén-me shí-jiān" means "what time" as frequency of happening

(shen me shi hou )means when,it's a abtract time . ex:when will they come back? tomorrow (shen me shi jian )means what time.it's a detail time ex:what time will they come back? tormorrow 9;00