for 是介词,其后要跟名词,当后面出现动词时就需要变形为动名词ing形式
其实这是介词类的普遍规律用法,其他介词还有about,in,on,at,from,off等等.
给你简单举例一下:同一句话 ”到吃晚饭时间了”
可以说It's time for supper .
也可以说It's time for having dinner .
it's time to do sth.
it's time for sb. to do sth.
it's time for sth.
it's time for doing sth.
反正for是介词,后面要么跟名词,要么跟动名词(v.ing)
是it is time for sb. did sth.吧.....
it is time for sb to do sth.
介词后面加 v.ing