It's seven o'clock in the evening.It'time()dinner.A.in B.for C.at

It's seven o'clock in the evening.It's time (B.for) dinner.
现在是晚上七点.到吃晚餐的时间了.
It's time for sth,到了做某事的时间.这里要用介词for表示“对于……”.为什么不能用to呢？^_^用to的时候是用的动词不定式，而不是动词。这句话应该这么表达：It's time (to have) dinner. 也就是说to要和动词原形一起用。