I googled and found someone said Q1 was correct way to ask the day. But I still have doubt about this.
Q1: What day is tomorrow?
Q2: What day is it tomorrow?
Answer:
It's Tuesday or
Tomorrow is Tuesday.
Which question is correct?
Learn English – How to ask the day
questions
Best Answer
Either is legitimate and would be understood.
“What day is tomorrow?” appears to be more popular:
But neither is more popular than Jim’s suggestion above of “What’s tomorrow?”:
It’s difficult to know how much weight to give the graphs above. For one thing, “What’s tomorrow?” is much more flexible contextually. For example:
This response would not be legitimate for either of the other forms of this question.
If I had to speculate, I’d say that “What day is it tomorrow?” is avoided for a few reasons, including the suspicion mentioned in the comments above that it doesn’t sound quite right to pair the definitively present-sounding “is it” with the decidedly futuristic “tomorrow”. There’s also the simple fact that the word order causes the speaker to all but ask a different question (“What day is it . . .”) before asking the intended question (“. . . tomorrow?”).
In the end, probably having to do with the fact that the concept of tomorrow depends on a reference point of today, people are comfortable asking about it in the present tense.
Personally, if I wanted to know which day of the week it was going to be, I’d ask:
Like many things in English, there isn’t a hard and fast rule here. Choose what feels right to you.