Americans write MM/DD/YY but globally it is usually written DD/MM/YY. There is often confusion globally with the American style when the date is between 1-12 because these are also equivalent to months, however if the date is 13-31 it is obvious that this cannot refer to a month. As for how to say your birthday, it is "on the 19th of October" or "on October 19".

US: (check other countries for how they would do this) My birthday is 10/19. ("ten nineteen". I would usually use this if someone is asking me while they're filling out a form.) My birthday is October 19th. or My birthday is on October 19th. My birthday is October 19. (very informal). My birthday is the nineteenth day of October. (very, very, very overly formal).

josias da Silva I'm afraid that this is not correct.

Americans write there dates with the month first then the day, so you would say my birthday is on 10/19. This is written out as my birthday is on October nineteenth.

She’s birthday is on October nineteen