I'm no BMV expert, but I think that price she gave you was for the 2yr tag like OG was saying...because prior to your birthday you should purchase tags for the year anyways considering you will get hosed on your birthday if you get pulled over with the EXPIRED tags still showing. I'm pretty sure they do not charge you extra for getting the tags a little early, but then again I think they enjoy inconvenience at the BMV...I sure hope you don't get back dated a year for 17 days cause that's crazy talk.