when did you start class today是什么时态

when did you start class today是什么时态 英语时态知识 when did you start class today?为什么是过去式? when did you start to______? When did you start skating? When did you start out? when did you start your homework when did you start to learn english? when did you start （）(hiccup) 1.--- When did you start colleting stamps? 怎样回答When did you start school? What you did是什么时态 When did it start?