对时间用 when 或者 what time 提问。

笼统的时间用 when

具体几点用what time

what time is it now? 现在几点了？

what's the date today? 今天几号？

when did you have lunch? 几点吃的午饭？

when will you go to london? 你何时去伦敦？

how long have been here? 你来这里多久了？