the date

I would like to know why the preposition ‘on’ would be wrong in the following sentence:

Christmas holidays start[color=red] on the 22nd of December.

It is not wrong.

Really ? Because my English teacher said it was wrong to put ‘on’ before the date.

Use ‘in’ with the month, where no day is mentioned. (in December)

Use ‘on’ for the day (on 22nd of December - that specific day in December)

For more examples, see the explanation I wrote here:
Re: Weekdays

(You have a spacing error in your message above. There is NO space before a question mark.)

So the sentence I wrote is correct, right?

As Dozy said, yes.

Would it be correct to say : Christmas holiday start the 22nd of December?

‘Christmas holidays start the 22nd of December’ is okay, but ‘start on’ is preferable in formal contexts.