Thread:Superbike10/@comment-3153778-20121203040034

In the most recent episode, Gwen states that it's srping break meaning that December has long passed in the Ben 10 Universe. Alien Force had another Spring Break episode "Max Out" while Ben was 15. While offscreen, spring break for 16 year old Ben happend during Ultimate Alien's timespan since the show went through Ben and Gwen's 16 year old summer as well. The series later went into the new school year as well. Ultimate Alien ended sometime during Ben's 11th grade year (Junior Year) so for Gwen to once more say it's Spring Break, she and Ben are 17 now. It may have been offscreen, but this is how Max's birthday was in AF & UA.

So in General

AF Ben at 15 Spring Break

UA Ben at 16 (Spring Break was during either seasons 1 or 2 hinted by Jimmy Jones)

OV Ben at 17 Spring Break (Many Happy Returns) 