User blog comment:SmellyMelly06/Character ages.../@comment-1428930-20130529021904/@comment-26308-20130601093044

"Well judging by Viserys' comments and the time elapsed since Robert's Rebellion, Daenerys is 17 at the beginning of the TV series."

Nope. Dany was conceived one month before the Sack of King's Landing and born eight months later, so she's effectively a year younger than the Sack. In the TV series she appears to be 16 when it starts, 17 now, probably turning 18 sometime in Season 4.