很多时候在使用时没有太大的区别，若是一定要弄清区别，It is time to do sth着重的是表达该做什么了，It is time for sth更着重于强调时间。比如： It is time to have dinner. 意思是：该吃晚饭了。 It is time for dinner. 意思是：现在是晚饭时间了。
It is time to do sth和It is time for sth的区别就在于结构不同，意思是一样的，二者通常可以作为同义句互相转换。 例句： It is time to go to school. = It is time for school. 该去上学了。 It is time to have breakfast. =It is time for breakfast. 该吃早饭了。