Board Thread:General Discussion/@comment-27012333-20150923171731/@comment-15115821-20150928172911

OfficialBrandonF wrote: Should I put under the 12 for their age that they turn 13 in Dipper and Mabel vs. The Future? Like this:

12 (born August – September 1999) 13 (as of Dipper and Mabel vs. The Future) Why did we do that? The teaser clearly state that they are a week away from their birthday, there is no evidence that they will turn 13 during the episode, Alex himself said their birthday is during the last day of summer and Mabel says that summer is almost over. Last point, he also said the series will end on the last day of summer, meaning they won't turn 13 until the finale and this is obviously not the series finale (at least it's not being advertised as the finale) and the end cards support this (and Alex said the series will end on January)

TL:DR, unless this takes place within the span of a week, the won't turn 13 during this episode.