I was recently arrested for a DUI, and being a minor, i was also charged with possession of alcohol. As told by the magistrate, consumption and possession are under the same law now. When the warrant was faxed over, i noticed they had put my birth year as 1970, i pointed it out to them and they penciled in the correction. Later, after being released, i noticed my copy of the warrant still said 1970 as the birth year. I was told by a co-worker that my rights were violated as i did not receive an exact copy of my warrant.
The warrant you receive must put you on reasonable notice of the crime of which you are accused, meaning that typographical errors and the like are not grounds for dismissal unless they are so egregious as to deprive you of knowledge of what you need to defend. The law also allows the Commonwealth to amend the face of a warrant to correct errors such as in your date of birth.
At trial you can expect the Commonwealth to introduce evidence of your true age, possibly through testimony of the arresting officer as to statements you made or through a properly authenticated public document such as your DMV record.
DUI cases are complicated, though, and you may have many viable defenses. You should speak with a Virginia lawyer who has experience defending DUI cases and who can speak intelligently about the city or county in which you are charged.