为什么 the other day 做状语不用加介词，而 some other day 需要加 for 或 on？如：

She looed at the vendor who cheated her the other day with distaste.

而下面的句子却用介词：

What if you want to buy a Treasury bill on some other day?

Would you like to make an appointment for some other day?

但有时介词亦会没有。如：

I'll come some other day.

这里是属于介词省略的用法吗？ 谢谢老师解答！