오늘은 몇일며칠이에예요 ?

오늘은, 2012년 고9(or 구)월 22(이십 이)일이에예요.
제 생일은 안이에아니예요. 제 생일은 3(삼)월 16(십 육)일이에예요.
선생님당신는은요? 너당신 냉일생일는은 언제이에예요 ?

I think you are writing the Korean sentences what you have heard.

Your sentences are a little weird.

The wrong spells have any basis, however the sentences have higher levels.

* 며칠

When I was young, 며칠 have a different meaning with 몇 일.

They had the meanings of period of days and a specific day, repectively.

But 몇 일 is combined to 며칠, so "며칠" have the meanings all, and 며칠 is right word today.

* 2012년 9월 22일

Korean people use this form.

* 존댓말 vs. 반말

선생님 means teacher.

But when you call a unfamiliar person who seems older than you, you can use this word.

It have meaning of repect.

So this word is suited to 존댓말, especially highly 존댓말.

But you used "너" in next sentence. This word is 반말.

In my opinion, 당신 is natural in these sentences.

* ~은, ~는

The two words are same usage.

But according to the previous words, the selection between the words are decided.

The previous words are ended with 받침, then you have to use ~은.

However in other cases, you have to use ~는.

For example,

   ~은: 당신은, 여러분은, 곰은,  and so on

   ~는: 나는, 너는, 우리는, 개는, and so on

If you sound these words, then you can know about these differences easily.

Let me know how you are writing these Korean sentences, please.

I'm curious about it. ^^