Question

When is your birthday?

My birthday is April 19th.
My birthday is on April 19th.
It is April 19th.
It is on April 19th.

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There are 4 answers above.
Which answers are right?
Are all correct answers?
Which ones are commonly used?

Answer 1

The only one of those that is really awkward is "It is April 19th." The subject of the "it" is not clear.