it is time for class 也可以说it is time to class吗?介词可以互换?

it is time for sth
it is time (for sb 常常省略) to do sth.
通常说 it is time for class.就可以了.
不说it is time to class.因为class 作动词用时的意思是：
把...分类(或分等级)